diff --git a/packages/checkbox-group/src/LionCheckboxGroup.js b/packages/checkbox-group/src/LionCheckboxGroup.js
index 4a3e1046b..6708a0619 100644
--- a/packages/checkbox-group/src/LionCheckboxGroup.js
+++ b/packages/checkbox-group/src/LionCheckboxGroup.js
@@ -1,12 +1,13 @@
+import { LitElement } from '@lion/core';
 import { ChoiceGroupMixin } from '@lion/choice-input';
-import { LionFieldset } from '@lion/fieldset';
+import { FormGroupMixin } from '@lion/fieldset';
 
 /**
  * A wrapper around multiple checkboxes
  *
  * @extends {LionFieldset}
  */
-export class LionCheckboxGroup extends ChoiceGroupMixin(LionFieldset) {
+export class LionCheckboxGroup extends ChoiceGroupMixin(FormGroupMixin(LitElement)) {
   constructor() {
     super();
     this.multipleChoice = true;
diff --git a/packages/choice-input/src/ChoiceGroupMixin.js b/packages/choice-input/src/ChoiceGroupMixin.js
index 123d92ac1..6bc3d93be 100644
--- a/packages/choice-input/src/ChoiceGroupMixin.js
+++ b/packages/choice-input/src/ChoiceGroupMixin.js
@@ -5,12 +5,30 @@ export const ChoiceGroupMixin = dedupeMixin(
   superclass =>
     // eslint-disable-next-line
     class ChoiceGroupMixin extends FormRegistrarMixin(InteractionStateMixin(superclass)) {
+      static get properties() {
+        return {
+          /**
+           * @desc When false (default), modelValue and serializedValue will reflect the
+           * currently selected choice (usually a string). When true, modelValue will and
+           * serializedValue will be an array of strings.
+           * @type {boolean}
+           */
+          multipleChoice: {
+            type: Boolean,
+            attribute: 'multiple-choice',
+          },
+        };
+      }
+
       get modelValue() {
         const elems = this._getCheckedElements();
         if (this.multipleChoice) {
+          // TODO: holds for both modelValue and serializedValue of choiceInput:
+          // consider only allowing strings as values, in which case 'el.value' would suffice
+          // and choice-input could be simplified
           return elems.map(el => el.modelValue.value);
         }
-        return elems ? elems.modelValue.value : '';
+        return elems[0] ? elems[0].modelValue.value : '';
       }
 
       set modelValue(value) {
@@ -18,11 +36,19 @@ export const ChoiceGroupMixin = dedupeMixin(
       }
 
       get serializedValue() {
+        // We want to filter out disabled values out by default:
+        // The goal of serializing values could either be submitting state to a backend
+        // ot storing state in a backend. For this, only values that are entered by the end
+        // user are relevant, choice values are always defined by the Application Developer
+        // and known by the backend.
+
+        // Assuming values are always defined as strings, modelValues and serializedValues
+        // are the same.
         const elems = this._getCheckedElements();
         if (this.multipleChoice) {
-          return this.modelValue;
+          return elems.map(el => el.serializedValue.value);
         }
-        return elems ? elems.serializedValue : '';
+        return elems[0] ? elems[0].serializedValue.value : '';
       }
 
       set serializedValue(value) {
@@ -53,24 +79,22 @@ export const ChoiceGroupMixin = dedupeMixin(
        */
       addFormElement(child, indexToInsertAt) {
         this._throwWhenInvalidChildModelValue(child);
+        // TODO: nice to have or does it have a function (since names are meant as keys for
+        // formElements)?
         this.__delegateNameAttribute(child);
         super.addFormElement(child, indexToInsertAt);
       }
 
       /**
-       * @override from LionFieldset
+       * @override
        */
-      // eslint-disable-next-line class-methods-use-this
-      get _childrenCanHaveSameName() {
-        return true;
-      }
-
-      /**
-       * @override from LionFieldset
-       */
-      // eslint-disable-next-line class-methods-use-this
-      get _childNamesCanBeDuplicate() {
-        return true;
+      _getFromAllFormElements(property, filterCondition = () => true) {
+        // For modelValue and serializedValue, an exception should be made,
+        // The reset can be requested from children
+        if (property === 'modelValue' || property === 'serializedValue') {
+          return this[property];
+        }
+        return this.formElements.filter(filterCondition).map(el => el.property);
       }
 
       _throwWhenInvalidChildModelValue(child) {
@@ -108,7 +132,7 @@ export const ChoiceGroupMixin = dedupeMixin(
         if (target.checked === false) return;
 
         const groupName = target.name;
-        this.formElementsArray
+        this.formElements
           .filter(i => i.name === groupName)
           .forEach(choice => {
             if (choice !== target) {
@@ -119,11 +143,8 @@ export const ChoiceGroupMixin = dedupeMixin(
       }
 
       _getCheckedElements() {
-        const filtered = this.formElementsArray.filter(el => el.checked === true);
-        if (this.multipleChoice) {
-          return filtered;
-        }
-        return filtered.length > 0 ? filtered[0] : undefined;
+        // We want to filter out disabled values out by default
+        return this.formElements.filter(el => el.checked && !el.disabled);
       }
 
       async _setCheckedElements(value, check) {
@@ -131,12 +152,12 @@ export const ChoiceGroupMixin = dedupeMixin(
           await this.registrationReady;
         }
 
-        for (let i = 0; i < this.formElementsArray.length; i += 1) {
+        for (let i = 0; i < this.formElements.length; i += 1) {
           if (this.multipleChoice) {
-            this.formElementsArray[i].checked = value.includes(this.formElementsArray[i].value);
-          } else if (check(this.formElementsArray[i], value)) {
+            this.formElements[i].checked = value.includes(this.formElements[i].value);
+          } else if (check(this.formElements[i], value)) {
             // Allows checking against custom values e.g. formattedValue or serializedValue
-            this.formElementsArray[i].checked = true;
+            this.formElements[i].checked = true;
           }
         }
       }
diff --git a/packages/choice-input/test/ChoiceGroupMixin.test.js b/packages/choice-input/test/ChoiceGroupMixin.test.js
index c8566f6c2..5d1f01f32 100644
--- a/packages/choice-input/test/ChoiceGroupMixin.test.js
+++ b/packages/choice-input/test/ChoiceGroupMixin.test.js
@@ -1,20 +1,21 @@
-import { html } from '@lion/core';
-import { LionFieldset } from '@lion/fieldset';
+import { html, LitElement } from '@lion/core';
+import { FormGroupMixin } from '@lion/fieldset';
 import { LionInput } from '@lion/input';
 import { Required } from '@lion/validate';
 import { expect, fixture, nextFrame } from '@open-wc/testing';
 import { ChoiceGroupMixin } from '../src/ChoiceGroupMixin.js';
 import { ChoiceInputMixin } from '../src/ChoiceInputMixin.js';
+import '@lion/fieldset/lion-fieldset.js';
 
 describe('ChoiceGroupMixin', () => {
   before(() => {
     class ChoiceInput extends ChoiceInputMixin(LionInput) {}
     customElements.define('choice-group-input', ChoiceInput);
 
-    class ChoiceGroup extends ChoiceGroupMixin(LionFieldset) {}
+    class ChoiceGroup extends ChoiceGroupMixin(FormGroupMixin(LitElement)) {}
     customElements.define('choice-group', ChoiceGroup);
 
-    class ChoiceGroupMultiple extends ChoiceGroupMixin(LionFieldset) {
+    class ChoiceGroupMultiple extends ChoiceGroupMixin(FormGroupMixin(LitElement)) {
       constructor() {
         super();
         this.multipleChoice = true;
@@ -33,9 +34,9 @@ describe('ChoiceGroupMixin', () => {
     `);
     await nextFrame();
     expect(el.modelValue).to.equal('female');
-    el.formElementsArray[0].checked = true;
+    el.formElements[0].checked = true;
     expect(el.modelValue).to.equal('male');
-    el.formElementsArray[2].checked = true;
+    el.formElements[2].checked = true;
     expect(el.modelValue).to.equal('other');
   });
 
@@ -68,15 +69,15 @@ describe('ChoiceGroupMixin', () => {
     `);
     await nextFrame();
 
-    expect(el.formElementsArray[0].name).to.equal('gender');
-    expect(el.formElementsArray[1].name).to.equal('gender');
+    expect(el.formElements[0].name).to.equal('gender');
+    expect(el.formElements[1].name).to.equal('gender');
 
     const validChild = await fixture(html`
       <choice-group-input .choiceValue=${'male'}></choice-group-input>
     `);
     el.appendChild(validChild);
 
-    expect(el.formElementsArray[2].name).to.equal('gender');
+    expect(el.formElements[2].name).to.equal('gender');
   });
 
   it('throws if a child element with a different name than the group tries to register', async () => {
@@ -112,7 +113,7 @@ describe('ChoiceGroupMixin', () => {
     await el.updateComplete;
 
     expect(el.modelValue).to.equal('other');
-    expect(el.formElementsArray[2].checked).to.be.true;
+    expect(el.formElements[2].checked).to.be.true;
   });
 
   it('can handle complex data via choiceValue', async () => {
@@ -127,7 +128,7 @@ describe('ChoiceGroupMixin', () => {
     await nextFrame();
 
     expect(el.modelValue).to.equal(date);
-    el.formElementsArray[0].checked = true;
+    el.formElements[0].checked = true;
     expect(el.modelValue).to.deep.equal({ some: 'data' });
   });
 
@@ -141,7 +142,7 @@ describe('ChoiceGroupMixin', () => {
     await nextFrame();
 
     expect(el.modelValue).to.equal(0);
-    el.formElementsArray[1].checked = true;
+    el.formElements[1].checked = true;
     expect(el.modelValue).to.equal('');
   });
 
@@ -160,7 +161,7 @@ describe('ChoiceGroupMixin', () => {
     await nextFrame();
     expect(el.modelValue).to.equal('female');
     el.modelValue = 'other';
-    expect(el.formElementsArray[2].checked).to.be.true;
+    expect(el.formElements[2].checked).to.be.true;
   });
 
   it('expect child nodes to only fire one model-value-changed event per instance', async () => {
@@ -180,14 +181,14 @@ describe('ChoiceGroupMixin', () => {
     await nextFrame();
     counter = 0; // reset after setup which may result in different results
 
-    el.formElementsArray[0].checked = true;
+    el.formElements[0].checked = true;
     expect(counter).to.equal(2); // male becomes checked, female becomes unchecked
 
     // not changed values trigger no event
-    el.formElementsArray[0].checked = true;
+    el.formElements[0].checked = true;
     expect(counter).to.equal(2);
 
-    el.formElementsArray[2].checked = true;
+    el.formElements[2].checked = true;
     expect(counter).to.equal(4); // other becomes checked, male becomes unchecked
 
     // not found values trigger no event
@@ -211,12 +212,12 @@ describe('ChoiceGroupMixin', () => {
     expect(el.validationStates).to.have.a.property('error');
     expect(el.validationStates.error).to.have.a.property('Required');
 
-    el.formElementsArray[0].checked = true;
+    el.formElements[0].checked = true;
     expect(el.hasFeedbackFor).not.to.include('error');
     expect(el.validationStates).to.have.a.property('error');
     expect(el.validationStates.error).not.to.have.a.property('Required');
 
-    el.formElementsArray[1].checked = true;
+    el.formElements[1].checked = true;
     expect(el.hasFeedbackFor).not.to.include('error');
     expect(el.validationStates).to.have.a.property('error');
     expect(el.validationStates.error).not.to.have.a.property('Required');
@@ -229,8 +230,8 @@ describe('ChoiceGroupMixin', () => {
         <choice-group-input .choiceValue=${'female'}></choice-group-input>
       </choice-group>
     `);
-    el.formElementsArray[0].checked = true;
-    expect(el.serializedValue).to.deep.equal({ checked: true, value: 'male' });
+    el.formElements[0].checked = true;
+    expect(el.serializedValue).to.deep.equal('male');
   });
 
   it('returns serialized value on unchecked state', async () => {
@@ -256,9 +257,9 @@ describe('ChoiceGroupMixin', () => {
       `);
       await nextFrame();
       expect(el.modelValue).to.eql(['female']);
-      el.formElementsArray[0].checked = true;
+      el.formElements[0].checked = true;
       expect(el.modelValue).to.eql(['male', 'female']);
-      el.formElementsArray[2].checked = true;
+      el.formElements[2].checked = true;
       expect(el.modelValue).to.eql(['male', 'female', 'other']);
     });
 
@@ -276,8 +277,8 @@ describe('ChoiceGroupMixin', () => {
       await el.updateComplete;
       el.modelValue = ['male', 'other'];
       expect(el.modelValue).to.eql(['male', 'other']);
-      expect(el.formElementsArray[0].checked).to.be.true;
-      expect(el.formElementsArray[2].checked).to.be.true;
+      expect(el.formElements[0].checked).to.be.true;
+      expect(el.formElements[2].checked).to.be.true;
     });
 
     it('unchecks non-matching checkboxes when setting the modelValue', async () => {
@@ -293,13 +294,40 @@ describe('ChoiceGroupMixin', () => {
       await el.registrationReady;
       await el.updateComplete;
       expect(el.modelValue).to.eql(['male', 'other']);
-      expect(el.formElementsArray[0].checked).to.be.true;
-      expect(el.formElementsArray[2].checked).to.be.true;
+      expect(el.formElements[0].checked).to.be.true;
+      expect(el.formElements[2].checked).to.be.true;
 
       el.modelValue = ['female'];
-      expect(el.formElementsArray[0].checked).to.be.false;
-      expect(el.formElementsArray[1].checked).to.be.true;
-      expect(el.formElementsArray[2].checked).to.be.false;
+      expect(el.formElements[0].checked).to.be.false;
+      expect(el.formElements[1].checked).to.be.true;
+      expect(el.formElements[2].checked).to.be.false;
+    });
+  });
+
+  describe('Integration with a parent form/fieldset', () => {
+    it('will serialize all children with their serializedValue', async () => {
+      const el = await fixture(html`
+        <lion-fieldset>
+          <choice-group name="gender">
+            <choice-group-input .choiceValue=${'male'} checked disabled></choice-group-input>
+            <choice-group-input .choiceValue=${'female'} checked></choice-group-input>
+            <choice-group-input .choiceValue=${'other'}></choice-group-input>
+          </choice-group>
+        </lion-fieldset>
+      `);
+
+      await nextFrame();
+      await el.registrationReady;
+      await el.updateComplete;
+      expect(el.serializedValue).to.eql({
+        gender: 'female',
+      });
+
+      const choiceGroupEl = el.querySelector('[name="gender"]');
+      choiceGroupEl.multipleChoice = true;
+      expect(el.serializedValue).to.eql({
+        gender: ['female'],
+      });
     });
   });
 });
diff --git a/packages/field/index.js b/packages/field/index.js
index 3dff79439..6c1d2d28d 100644
--- a/packages/field/index.js
+++ b/packages/field/index.js
@@ -1,9 +1,10 @@
-export { FieldCustomMixin } from './src/FieldCustomMixin.js';
 export { FocusMixin } from './src/FocusMixin.js';
 export { FormatMixin } from './src/FormatMixin.js';
+export { FieldCustomMixin } from './src/FieldCustomMixin.js';
 export { FormControlMixin } from './src/FormControlMixin.js';
 export { InteractionStateMixin } from './src/InteractionStateMixin.js'; // applies FocusMixin
 export { LionField } from './src/LionField.js';
-export { FormRegisteringMixin } from './src/FormRegisteringMixin.js';
-export { FormRegistrarMixin } from './src/FormRegistrarMixin.js';
-export { FormRegistrarPortalMixin } from './src/FormRegistrarPortalMixin.js';
+export { FormRegisteringMixin } from './src/registration/FormRegisteringMixin.js';
+export { FormRegistrarMixin } from './src/registration/FormRegistrarMixin.js';
+export { FormRegistrarPortalMixin } from './src/registration/FormRegistrarPortalMixin.js';
+export { FormControlsCollection } from './src/registration/FormControlsCollection.js';
diff --git a/packages/field/src/FormControlMixin.js b/packages/field/src/FormControlMixin.js
index c58717615..6cfd78a90 100644
--- a/packages/field/src/FormControlMixin.js
+++ b/packages/field/src/FormControlMixin.js
@@ -1,5 +1,5 @@
 import { html, css, nothing, dedupeMixin, SlotMixin } from '@lion/core';
-import { FormRegisteringMixin } from './FormRegisteringMixin.js';
+import { FormRegisteringMixin } from './registration/FormRegisteringMixin.js';
 import { getAriaElementsInRightDomOrder } from './utils/getAriaElementsInRightDomOrder.js';
 
 /**
@@ -28,11 +28,18 @@ export const FormControlMixin = dedupeMixin(
     class FormControlMixin extends FormRegisteringMixin(SlotMixin(superclass)) {
       static get properties() {
         return {
+          /**
+           * The name the element will be registered on to the .formElements collection
+           * of the parent.
+           */
+          name: {
+            type: String,
+            reflect: true,
+          },
           /**
            * When no light dom defined and prop set
            */
           label: String,
-
           /**
            * When no light dom defined and prop set
            */
@@ -40,12 +47,10 @@ export const FormControlMixin = dedupeMixin(
             type: String,
             attribute: 'help-text',
           },
-
           /**
            * Contains all elements that should end up in aria-labelledby of `._inputNode`
            */
           _ariaLabelledNodes: Array,
-
           /**
            * Contains all elements that should end up in aria-describedby of `._inputNode`
            */
@@ -73,6 +78,14 @@ export const FormControlMixin = dedupeMixin(
         this.requestUpdate('helpText', oldValue);
       }
 
+      set fieldName(value) {
+        this.__fieldName = value;
+      }
+
+      get fieldName() {
+        return this.__fieldName || this.label || this.name;
+      }
+
       get slots() {
         return {
           ...super.slots,
@@ -146,9 +159,6 @@ export const FormControlMixin = dedupeMixin(
         this._enhanceLightDomA11y();
       }
 
-      /**
-       * Public methods
-       */
       _enhanceLightDomClasses() {
         if (this._inputNode) {
           this._inputNode.classList.add('form-control');
diff --git a/packages/field/src/FormRegistrarMixin.js b/packages/field/src/FormRegistrarMixin.js
deleted file mode 100644
index bb341805a..000000000
--- a/packages/field/src/FormRegistrarMixin.js
+++ /dev/null
@@ -1,121 +0,0 @@
-import { dedupeMixin } from '@lion/core';
-import { FormRegisteringMixin } from './FormRegisteringMixin.js';
-import { formRegistrarManager } from './formRegistrarManager.js';
-
-/**
- * This allows an element to become the manager of a register
- */
-export const FormRegistrarMixin = dedupeMixin(
-  superclass =>
-    // eslint-disable-next-line no-shadow, no-unused-vars
-    class FormRegistrarMixin extends FormRegisteringMixin(superclass) {
-      get formElements() {
-        return this.__formElements;
-      }
-
-      set formElements(value) {
-        this.__formElements = value;
-      }
-
-      get formElementsArray() {
-        return this.__formElements;
-      }
-
-      constructor() {
-        super();
-        this.formElements = [];
-        this.__readyForRegistration = false;
-        this.__hasBeenRendered = false;
-        this.registrationReady = new Promise(resolve => {
-          this.__resolveRegistrationReady = resolve;
-        });
-
-        this._onRequestToAddFormElement = this._onRequestToAddFormElement.bind(this);
-        this.addEventListener('form-element-register', this._onRequestToAddFormElement);
-      }
-
-      connectedCallback() {
-        if (super.connectedCallback) {
-          super.connectedCallback();
-        }
-        formRegistrarManager.add(this);
-        if (this.__hasBeenRendered) {
-          formRegistrarManager.becomesReady();
-        }
-      }
-
-      disconnectedCallback() {
-        if (super.disconnectedCallback) {
-          super.disconnectedCallback();
-        }
-        formRegistrarManager.remove(this);
-      }
-
-      isRegisteredFormElement(el) {
-        return this.formElementsArray.some(exitingEl => exitingEl === el);
-      }
-
-      firstUpdated(changedProperties) {
-        super.firstUpdated(changedProperties);
-        this.__resolveRegistrationReady();
-        this.__readyForRegistration = true;
-        formRegistrarManager.becomesReady();
-        this.__hasBeenRendered = true;
-      }
-
-      addFormElement(child, index) {
-        // This is a way to let the child element (a lion-fieldset or lion-field) know, about its parent
-        // eslint-disable-next-line no-param-reassign
-        child.__parentFormGroup = this;
-
-        if (index > 0) {
-          this.formElements.splice(index, 0, child);
-        } else {
-          this.formElements.push(child);
-        }
-      }
-
-      removeFormElement(child) {
-        const index = this.formElements.indexOf(child);
-        if (index > -1) {
-          this.formElements.splice(index, 1);
-        }
-      }
-
-      _onRequestToAddFormElement(ev) {
-        const child = ev.detail.element;
-        if (child === this) {
-          // as we fire and listen - don't add ourselves
-          return;
-        }
-        if (this.isRegisteredFormElement(child)) {
-          // do not readd already existing elements
-          return;
-        }
-        ev.stopPropagation();
-
-        // Check for siblings to determine the right order to insert into formElements
-        // If there is no next sibling, index is -1
-        let indexToInsertAt = -1;
-        if (this.formElements && Array.isArray(this.formElements)) {
-          indexToInsertAt = this.formElements.indexOf(child.nextElementSibling);
-        }
-        this.addFormElement(child, indexToInsertAt);
-      }
-
-      _onRequestToRemoveFormElement(ev) {
-        const child = ev.detail.element;
-        if (child === this) {
-          // as we fire and listen - don't add ourselves
-          return;
-        }
-        if (!this.isRegisteredFormElement(child)) {
-          // do not readd already existing elements
-          return;
-        }
-        ev.stopPropagation();
-
-        this.removeFormElement(child);
-      }
-    },
-);
diff --git a/packages/field/src/registration/FormControlsCollection.js b/packages/field/src/registration/FormControlsCollection.js
new file mode 100644
index 000000000..f425588ad
--- /dev/null
+++ b/packages/field/src/registration/FormControlsCollection.js
@@ -0,0 +1,98 @@
+/**
+ * @desc This class closely mimics the natively
+ * supported HTMLFormControlsCollection. It can be accessed
+ * both like an array and an object (based on control/element names).
+ * @example
+ * // This is how a native form works:
+ * <form>
+ *   <input id="a" name="a">
+ *   <fieldset>
+ *      <input id="b1" name="b[]">
+ *      <input id="b2" name="b[]">
+ *      <input id="c" name="c">
+ *   </fieldset>
+ *   <select id="d" name="d">
+ *     <option></option>
+ *   </select>
+ *   <fieldset>
+ *     <input type="radio" id="e1" name="e">
+ *     <input type="radio" id="e2" name="e">
+ *   </fieldset>
+ *   <select id="f" name="f" multiple>
+ *     <option></option>
+ *   </select>
+ *   <fieldset>
+ *     <input type="checkbox" id="g1" name="g">
+ *     <input type="checkbox" id="g2" name="g">
+ *   </fieldset>
+ * </form>
+ *
+ * form.elements[0]; // Element input#a
+ * form.elements[1]; // Element input#b1
+ * form.elements[2]; // Element input#b2
+ * form.elements[3]; // Element input#c
+ * form.elements.a;  // Element input#a
+ * form.elements.b;  // RadioNodeList<Element> [input#b1, input#b2]
+ * form.elements.c;  // input#c
+ *
+ * // This is how a Lion form works (for simplicity Lion components have the 'l'-prefix):
+ * <l-form>
+ *  <form>
+ *
+ *    <!-- fields -->
+ *
+ *    <l-input id="a" name="a"></l-input>
+ *
+ *
+ *    <!-- field sets ('sub forms') -->
+ *
+ *    <l-fieldset>
+ *      <l-input id="b1" name="b"</l-input>
+ *      <l-input id="b2" name="b"></l-input>
+ *      <l-input id="c" name="c"></l-input>
+ *    </l-fieldset>
+ *
+ *
+ *    <!-- choice groups (children are 'end points') -->
+ *
+ *    <!-- single selection choice groups -->
+ *    <l-select id="d" name="d">
+ *      <l-option></l-option>
+ *    </l-select>
+ *    <l-radio-group id="e" name="e">
+ *      <l-radio></l-radio>
+ *      <l-radio></l-radio>
+ *    </l-radio-group>
+ *
+ *    <!-- multi selection choice groups -->
+ *    <l-select id="f" name="f" multiple>
+ *      <l-option></l-option>
+ *    </l-select>
+ *    <l-checkbox-group id="g" name="g">
+ *      <l-checkbox></l-checkbox>
+ *      <l-checkbox></l-checkbox>
+ *    </l-checkbox-group>
+ *
+ *  </form>
+ * </l-form>
+ *
+ * lionForm.formElements[0];                  // Element l-input#a
+ * lionForm.formElements[1];                  // Element l-input#b1
+ * lionForm.formElements[2];                  // Element l-input#b2
+ * lionForm.formElements.a;                   // Element l-input#a
+ * lionForm.formElements['b[]'];              // Array<Element> [l-input#b1, l-input#b2]
+ * lionForm.formElements.c;                   // Element l-input#c
+ *
+ * lionForm.formElements[d-g].formElements; // Array<Element>
+ *
+ * lionForm.formElements[d-e].value;          // String
+ * lionForm.formElements[f-g].value;          // Array<String>
+ */
+export class FormControlsCollection extends Array {
+  /**
+   * @desc Gives back the named keys and filters out array indexes
+   */
+  keys() {
+    return Object.keys(this).filter(k => Number.isNaN(Number(k)));
+  }
+}
diff --git a/packages/field/src/FormRegisteringMixin.js b/packages/field/src/registration/FormRegisteringMixin.js
similarity index 100%
rename from packages/field/src/FormRegisteringMixin.js
rename to packages/field/src/registration/FormRegisteringMixin.js
diff --git a/packages/field/src/registration/FormRegistrarMixin.js b/packages/field/src/registration/FormRegistrarMixin.js
new file mode 100644
index 000000000..e98bf0a28
--- /dev/null
+++ b/packages/field/src/registration/FormRegistrarMixin.js
@@ -0,0 +1,184 @@
+// eslint-disable-next-line max-classes-per-file
+import { dedupeMixin } from '@lion/core';
+import { FormRegisteringMixin } from './FormRegisteringMixin.js';
+import { formRegistrarManager } from './formRegistrarManager.js';
+import { FormControlsCollection } from './FormControlsCollection.js';
+
+// TODO: rename .formElements to .formControls? (or .$controls ?)
+
+/**
+ * @desc This allows an element to become the manager of a register.
+ * It basically keeps track of a FormControlsCollection that it stores in .formElements
+ * This will always be an array of all elements.
+ * In case of a form or fieldset(sub form), it will also act as a key based object with FormControl
+ * (fields, choice groups or fieldsets)as keys.
+ * For choice groups, the value will only stay an array.
+ * See FormControlsCollection for more information
+ */
+export const FormRegistrarMixin = dedupeMixin(
+  superclass =>
+    // eslint-disable-next-line no-shadow, no-unused-vars
+    class FormRegistrarMixin extends FormRegisteringMixin(superclass) {
+      static get properties() {
+        return {
+          /**
+           * @desc Flag that determines how ".formElements" should behave.
+           * For a regular fieldset (see LionFieldset) we expect ".formElements"
+           * to be accessible as an object.
+           * In case of a radio-group, a checkbox-group or a select/listbox,
+           * it should act like an array (see ChoiceGroupMixin).
+           * Usually, when false, we deal with a choice-group (radio-group, checkbox-group,
+           * (multi)select)
+           * @type {boolean}
+           */
+          _isFormOrFieldset: Boolean,
+        };
+      }
+
+      constructor() {
+        super();
+        this.formElements = new FormControlsCollection();
+
+        this._isFormOrFieldset = false;
+
+        this.__readyForRegistration = false;
+        this.__hasBeenRendered = false;
+        this.registrationReady = new Promise(resolve => {
+          this.__resolveRegistrationReady = resolve;
+        });
+
+        this._onRequestToAddFormElement = this._onRequestToAddFormElement.bind(this);
+        this.addEventListener('form-element-register', this._onRequestToAddFormElement);
+      }
+
+      connectedCallback() {
+        if (super.connectedCallback) {
+          super.connectedCallback();
+        }
+        formRegistrarManager.add(this);
+        if (this.__hasBeenRendered) {
+          formRegistrarManager.becomesReady();
+        }
+      }
+
+      disconnectedCallback() {
+        if (super.disconnectedCallback) {
+          super.disconnectedCallback();
+        }
+        formRegistrarManager.remove(this);
+      }
+
+      isRegisteredFormElement(el) {
+        return this.formElements.some(exitingEl => exitingEl === el);
+      }
+
+      firstUpdated(changedProperties) {
+        super.firstUpdated(changedProperties);
+        this.__resolveRegistrationReady();
+        this.__readyForRegistration = true;
+        formRegistrarManager.becomesReady();
+        this.__hasBeenRendered = true;
+      }
+
+      addFormElement(child, indexToInsertAt) {
+        // This is a way to let the child element (a lion-fieldset or lion-field) know, about its parent
+        // eslint-disable-next-line no-param-reassign
+        child.__parentFormGroup = this;
+
+        // 1. Add children as array element
+        if (indexToInsertAt > 0) {
+          this.formElements.splice(indexToInsertAt, 0, child);
+        } else {
+          this.formElements.push(child);
+        }
+
+        // 2. Add children as object key
+        if (this._isFormOrFieldset) {
+          const { name } = child;
+          if (!name) {
+            console.info('Error Node:', child); // eslint-disable-line no-console
+            throw new TypeError('You need to define a name');
+          }
+          if (name === this.name) {
+            console.info('Error Node:', child); // eslint-disable-line no-console
+            throw new TypeError(`You can not have the same name "${name}" as your parent`);
+          }
+
+          if (name.substr(-2) === '[]') {
+            if (!Array.isArray(this.formElements[name])) {
+              this.formElements[name] = new FormControlsCollection();
+            }
+            if (indexToInsertAt > 0) {
+              this.formElements[name].splice(indexToInsertAt, 0, child);
+            } else {
+              this.formElements[name].push(child);
+            }
+          } else if (!this.formElements[name]) {
+            this.formElements[name] = child;
+          } else {
+            console.info('Error Node:', child); // eslint-disable-line no-console
+            throw new TypeError(
+              `Name "${name}" is already registered - if you want an array add [] to the end`,
+            );
+          }
+        }
+      }
+
+      removeFormElement(child) {
+        // 1. Handle array based children
+        const index = this.formElements.indexOf(child);
+        if (index > -1) {
+          this.formElements.splice(index, 1);
+        }
+
+        // 2. Handle name based object keys
+        if (this._isFormOrFieldset) {
+          const { name } = child;
+          if (name.substr(-2) === '[]' && this.formElements[name]) {
+            const idx = this.formElements[name].indexOf(child);
+            if (idx > -1) {
+              this.formElements[name].splice(idx, 1);
+            }
+          } else if (this.formElements[name]) {
+            delete this.formElements[name];
+          }
+        }
+      }
+
+      _onRequestToAddFormElement(ev) {
+        const child = ev.detail.element;
+        if (child === this) {
+          // as we fire and listen - don't add ourselves
+          return;
+        }
+        if (this.isRegisteredFormElement(child)) {
+          // do not readd already existing elements
+          return;
+        }
+        ev.stopPropagation();
+
+        // Check for siblings to determine the right order to insert into formElements
+        // If there is no next sibling, index is -1
+        let indexToInsertAt = -1;
+        if (this.formElements && Array.isArray(this.formElements)) {
+          indexToInsertAt = this.formElements.indexOf(child.nextElementSibling);
+        }
+        this.addFormElement(child, indexToInsertAt);
+      }
+
+      _onRequestToRemoveFormElement(ev) {
+        const child = ev.detail.element;
+        if (child === this) {
+          // as we fire and listen - don't remove ourselves
+          return;
+        }
+        if (!this.isRegisteredFormElement(child)) {
+          // do not remove non existing elements
+          return;
+        }
+        ev.stopPropagation();
+
+        this.removeFormElement(child);
+      }
+    },
+);
diff --git a/packages/field/src/FormRegistrarPortalMixin.js b/packages/field/src/registration/FormRegistrarPortalMixin.js
similarity index 100%
rename from packages/field/src/FormRegistrarPortalMixin.js
rename to packages/field/src/registration/FormRegistrarPortalMixin.js
diff --git a/packages/field/src/formRegistrarManager.js b/packages/field/src/registration/formRegistrarManager.js
similarity index 100%
rename from packages/field/src/formRegistrarManager.js
rename to packages/field/src/registration/formRegistrarManager.js
diff --git a/packages/field/test-suites/FormRegistrationMixins.suite.js b/packages/field/test-suites/FormRegistrationMixins.suite.js
index 871dfd4a3..6d06949d9 100644
--- a/packages/field/test-suites/FormRegistrationMixins.suite.js
+++ b/packages/field/test-suites/FormRegistrationMixins.suite.js
@@ -1,19 +1,18 @@
 import { LitElement } from '@lion/core';
 import { defineCE, expect, fixture, html, unsafeStatic } from '@open-wc/testing';
 import sinon from 'sinon';
-import { FormRegisteringMixin } from '../src/FormRegisteringMixin.js';
-import { formRegistrarManager } from '../src/formRegistrarManager.js';
-import { FormRegistrarMixin } from '../src/FormRegistrarMixin.js';
-import { FormRegistrarPortalMixin } from '../src/FormRegistrarPortalMixin.js';
+import { FormRegisteringMixin } from '../src/registration/FormRegisteringMixin.js';
+import { formRegistrarManager } from '../src/registration/formRegistrarManager.js';
+import { FormRegistrarMixin } from '../src/registration/FormRegistrarMixin.js';
+import { FormRegistrarPortalMixin } from '../src/registration/FormRegistrarPortalMixin.js';
 
 export const runRegistrationSuite = customConfig => {
   const cfg = {
     baseElement: HTMLElement,
-    suffix: null,
     ...customConfig,
   };
 
-  describe(`FormRegistrationMixins${cfg.suffix ? ` (${cfg.suffix})` : ''}`, () => {
+  describe('FormRegistrationMixins', () => {
     let parentTag;
     let childTag;
     let portalTag;
diff --git a/packages/fieldset/index.js b/packages/fieldset/index.js
index ea598fcfd..5b8206ecb 100644
--- a/packages/fieldset/index.js
+++ b/packages/fieldset/index.js
@@ -1 +1,2 @@
 export { LionFieldset } from './src/LionFieldset.js';
+export { FormGroupMixin } from './src/FormGroupMixin.js';
diff --git a/packages/fieldset/src/FormGroupMixin.js b/packages/fieldset/src/FormGroupMixin.js
new file mode 100644
index 000000000..1b3b771ba
--- /dev/null
+++ b/packages/fieldset/src/FormGroupMixin.js
@@ -0,0 +1,403 @@
+import { html, dedupeMixin, SlotMixin } from '@lion/core';
+import { DisabledMixin } from '@lion/core/src/DisabledMixin.js';
+import { FormControlMixin, FormRegistrarMixin, FormControlsCollection } from '@lion/field';
+import { getAriaElementsInRightDomOrder } from '@lion/field/src/utils/getAriaElementsInRightDomOrder.js';
+import { ValidateMixin } from '@lion/validate';
+import { FormElementsHaveNoError } from './FormElementsHaveNoError.js';
+
+/**
+ * @desc Form group mixin serves as the basis for (sub) forms. Designed to be put on
+ * elements with role=group (or radiogroup)
+ * It bridges all the functionality of the child form controls:
+ * ValidateMixin, InteractionStateMixin, FormatMixin, FormControlMixin etc.
+ * It is designed to be used on top of FormRegstrarMixin and ChoiceGroupMixin
+ * Also, the LionFieldset element (which supports name based retrieval of children via formElements
+ * and the automatic grouping of formElements via '[]')
+ *
+ */
+export const FormGroupMixin = dedupeMixin(
+  superclass =>
+    // eslint-disable-next-line no-shadow
+    class FormGroupMixin extends FormRegistrarMixin(
+      FormControlMixin(ValidateMixin(DisabledMixin(SlotMixin(superclass)))),
+    ) {
+      static get properties() {
+        return {
+          /**
+           * Interaction state that can be used to compute the visibility of
+           * feedback messages
+           */
+          // TODO: Move property submitted to InteractionStateMixin.
+          submitted: {
+            type: Boolean,
+            reflect: true,
+          },
+          /**
+           * Interaction state that will be active when any of the children
+           * is focused.
+           */
+          focused: {
+            type: Boolean,
+            reflect: true,
+          },
+          /**
+           * Interaction state that will be active when any of the children
+           * is dirty (see InteractionStateMixin for more details.)
+           */
+          dirty: {
+            type: Boolean,
+            reflect: true,
+          },
+          /**
+           * Interaction state that will be active when the group as a whole is
+           * blurred
+           */
+          touched: {
+            type: Boolean,
+            reflect: true,
+          },
+          /**
+           * Interaction state that will be active when all of the children
+           * are prefilled (see InteractionStateMixin for more details.)
+           */
+          prefilled: {
+            type: Boolean,
+            reflect: true,
+          },
+        };
+      }
+
+      get _inputNode() {
+        return this;
+      }
+
+      get modelValue() {
+        return this._getFromAllFormElements('modelValue');
+      }
+
+      set modelValue(values) {
+        this._setValueMapForAllFormElements('modelValue', values);
+      }
+
+      get serializedValue() {
+        return this._getFromAllFormElements('serializedValue');
+      }
+
+      set serializedValue(values) {
+        this._setValueMapForAllFormElements('serializedValue', values);
+      }
+
+      get formattedValue() {
+        return this._getFromAllFormElements('formattedValue');
+      }
+
+      set formattedValue(values) {
+        this._setValueMapForAllFormElements('formattedValue', values);
+      }
+
+      // TODO: should it be any or every? Should we maybe keep track of both,
+      // so we can configure feedback visibility depending on scenario?
+      // Should we allow configuring feedback visibility on validator instances
+      // for maximal flexibility?
+      // Document this...
+      get prefilled() {
+        return this._everyFormElementHas('prefilled');
+      }
+
+      constructor() {
+        super();
+        this.disabled = false;
+        this.submitted = false;
+        this.dirty = false;
+        this.touched = false;
+        this.focused = false;
+        this.__addedSubValidators = false;
+
+        this._checkForOutsideClick = this._checkForOutsideClick.bind(this);
+
+        this.addEventListener('focusin', this._syncFocused);
+        this.addEventListener('focusout', this._onFocusOut);
+        this.addEventListener('dirty-changed', this._syncDirty);
+        this.addEventListener('validate-performed', this.__onChildValidatePerformed);
+
+        this.defaultValidators = [new FormElementsHaveNoError()];
+      }
+
+      connectedCallback() {
+        // eslint-disable-next-line wc/guard-super-call
+        super.connectedCallback();
+        this.setAttribute('role', 'group');
+        this.__initInteractionStates();
+      }
+
+      disconnectedCallback() {
+        super.disconnectedCallback(); // eslint-disable-line wc/guard-super-call
+
+        if (this.__hasActiveOutsideClickHandling) {
+          document.removeEventListener('click', this._checkForOutsideClick);
+          this.__hasActiveOutsideClickHandling = false;
+        }
+      }
+
+      async __initInteractionStates() {
+        if (!this.__readyForRegistration) {
+          await this.registrationReady;
+        }
+        this.formElements.forEach(el => {
+          if (typeof el.initInteractionState === 'function') {
+            el.initInteractionState();
+          }
+        });
+      }
+
+      updated(changedProps) {
+        super.updated(changedProps);
+
+        if (changedProps.has('disabled')) {
+          if (this.disabled) {
+            this.__requestChildrenToBeDisabled();
+          } else {
+            this.__retractRequestChildrenToBeDisabled();
+          }
+        }
+
+        if (changedProps.has('focused')) {
+          if (this.focused === true) {
+            this.__setupOutsideClickHandling();
+          }
+        }
+      }
+
+      __setupOutsideClickHandling() {
+        if (!this.__hasActiveOutsideClickHandling) {
+          document.addEventListener('click', this._checkForOutsideClick);
+          this.__hasActiveOutsideClickHandling = true;
+        }
+      }
+
+      _checkForOutsideClick(event) {
+        const outsideGroupClicked = !this.contains(event.target);
+        if (outsideGroupClicked) {
+          this.touched = true;
+        }
+      }
+
+      __requestChildrenToBeDisabled() {
+        this.formElements.forEach(child => {
+          if (child.makeRequestToBeDisabled) {
+            child.makeRequestToBeDisabled();
+          }
+        });
+      }
+
+      __retractRequestChildrenToBeDisabled() {
+        this.formElements.forEach(child => {
+          if (child.retractRequestToBeDisabled) {
+            child.retractRequestToBeDisabled();
+          }
+        });
+      }
+
+      // eslint-disable-next-line class-methods-use-this
+      inputGroupTemplate() {
+        return html`
+          <div class="input-group">
+            <slot></slot>
+          </div>
+        `;
+      }
+
+      /**
+       * @desc Handles interaction state 'submitted'.
+       * This allows children to enable visibility of validation feedback
+       */
+      submitGroup() {
+        this.submitted = true;
+        this.formElements.forEach(child => {
+          if (typeof child.submitGroup === 'function') {
+            child.submitGroup();
+          } else {
+            child.submitted = true; // eslint-disable-line no-param-reassign
+          }
+        });
+      }
+
+      resetGroup() {
+        this.formElements.forEach(child => {
+          if (typeof child.resetGroup === 'function') {
+            child.resetGroup();
+          } else if (typeof child.reset === 'function') {
+            child.reset();
+          }
+        });
+
+        this.resetInteractionState();
+      }
+
+      resetInteractionState() {
+        this.submitted = false;
+        this.touched = false;
+        this.dirty = false;
+        this.formElements.forEach(formElement => {
+          if (typeof formElement.resetInteractionState === 'function') {
+            formElement.resetInteractionState();
+          }
+        });
+      }
+
+      _getFromAllFormElements(property, filterCondition = el => !el.disabled) {
+        const result = {};
+        this.formElements.keys().forEach(name => {
+          const elem = this.formElements[name];
+          if (elem instanceof FormControlsCollection) {
+            result[name] = elem.filter(el => filterCondition(el)).map(el => el[property]);
+          } else if (filterCondition(elem)) {
+            if (typeof elem._getFromAllFormElements === 'function') {
+              result[name] = elem._getFromAllFormElements(property, filterCondition);
+            } else {
+              result[name] = elem[property];
+            }
+          }
+        });
+        return result;
+      }
+
+      _setValueForAllFormElements(property, value) {
+        this.formElements.forEach(el => {
+          el[property] = value; // eslint-disable-line no-param-reassign
+        });
+      }
+
+      async _setValueMapForAllFormElements(property, values) {
+        if (!this.__readyForRegistration) {
+          await this.registrationReady;
+        }
+
+        if (values && typeof values === 'object') {
+          Object.keys(values).forEach(name => {
+            if (Array.isArray(this.formElements[name])) {
+              this.formElements[name].forEach((el, index) => {
+                el[property] = values[name][index]; // eslint-disable-line no-param-reassign
+              });
+            }
+            this.formElements[name][property] = values[name];
+          });
+        }
+      }
+
+      _anyFormElementHas(property) {
+        return Object.keys(this.formElements).some(name => {
+          if (Array.isArray(this.formElements[name])) {
+            return this.formElements[name].some(el => !!el[property]);
+          }
+          return !!this.formElements[name][property];
+        });
+      }
+
+      _anyFormElementHasFeedbackFor(state) {
+        return Object.keys(this.formElements).some(name => {
+          if (Array.isArray(this.formElements[name])) {
+            return this.formElements[name].some(el => !!el.hasFeedbackFor.includes(state));
+          }
+          return !!this.formElements[name].hasFeedbackFor.includes(state);
+        });
+      }
+
+      _everyFormElementHas(property) {
+        return Object.keys(this.formElements).every(name => {
+          if (Array.isArray(this.formElements[name])) {
+            return this.formElements[name].every(el => !!el[property]);
+          }
+          return !!this.formElements[name][property];
+        });
+      }
+
+      /**
+       * Gets triggered by event 'validate-performed' which enabled us to handle 2 different situations
+       *   - react on modelValue change, which says something about the validity as a whole
+       *       (at least two checkboxes for instance) and nothing about the children's values
+       *   - children validity states have changed, so fieldset needs to update itself based on that
+       */
+      __onChildValidatePerformed(ev) {
+        if (ev && this.isRegisteredFormElement(ev.target)) {
+          this.validate();
+        }
+      }
+
+      _syncFocused() {
+        this.focused = this._anyFormElementHas('focused');
+      }
+
+      _onFocusOut(ev) {
+        const lastEl = this.formElements[this.formElements.length - 1];
+        if (ev.target === lastEl) {
+          this.touched = true;
+        }
+        this.focused = false;
+      }
+
+      _syncDirty() {
+        this.dirty = this._anyFormElementHas('dirty');
+      }
+
+      __linkChildrenMessagesToParent(child) {
+        // aria-describedby of (nested) children
+        let parent = this;
+        while (parent) {
+          this.constructor._addDescriptionElementIdsToField(
+            child,
+            parent._getAriaDescriptionElements(),
+          );
+          // Also check if the newly added child needs to refer grandparents
+          parent = parent.__parentFormGroup;
+        }
+      }
+
+      /**
+       * @override of FormRegistrarMixin.
+       * @desc Connects ValidateMixin and DisabledMixin
+       * On top of this, error messages of children are linked to their parents
+       */
+      addFormElement(child, indexToInsertAt) {
+        super.addFormElement(child, indexToInsertAt);
+        if (this.disabled) {
+          // eslint-disable-next-line no-param-reassign
+          child.makeRequestToBeDisabled();
+        }
+        // TODO: Unlink in removeFormElement
+        this.__linkChildrenMessagesToParent(child);
+        this.validate();
+      }
+
+      /**
+       * Gathers initial model values of all children. Used
+       * when resetGroup() is called.
+       */
+      get _initialModelValue() {
+        return this._getFromAllFormElements('_initialModelValue');
+      }
+
+      /**
+       * Add aria-describedby to child element(field), so that it points to feedback/help-text of
+       * parent(fieldset)
+       * @param {LionField} field - the child: lion-field/lion-input/lion-textarea
+       * @param {array} descriptionElements  - description elements like feedback and help-text
+       */
+      static _addDescriptionElementIdsToField(field, descriptionElements) {
+        const orderedEls = getAriaElementsInRightDomOrder(descriptionElements, { reverse: true });
+        orderedEls.forEach(el => {
+          if (field.addToAriaDescribedBy) {
+            field.addToAriaDescribedBy(el, { reorder: false });
+          }
+        });
+      }
+
+      /**
+       * @override of FormRegistrarMixin. Connects ValidateMixin
+       */
+      removeFormElement(...args) {
+        super.removeFormElement(...args);
+        this.validate();
+      }
+    },
+);
diff --git a/packages/fieldset/src/LionFieldset.js b/packages/fieldset/src/LionFieldset.js
index ece64a2a7..9ea5829d1 100644
--- a/packages/fieldset/src/LionFieldset.js
+++ b/packages/fieldset/src/LionFieldset.js
@@ -1,473 +1,29 @@
-import { html, LitElement, SlotMixin } from '@lion/core';
-import { DisabledMixin } from '@lion/core/src/DisabledMixin.js';
-import { FormControlMixin, FormRegistrarMixin } from '@lion/field';
-import { getAriaElementsInRightDomOrder } from '@lion/field/src/utils/getAriaElementsInRightDomOrder.js';
-import { ValidateMixin } from '@lion/validate';
-import { FormElementsHaveNoError } from './FormElementsHaveNoError.js';
+import { LitElement } from '@lion/core';
+import { FormGroupMixin } from './FormGroupMixin.js';
 
 /**
- * LionFieldset: fieldset wrapper providing extra features and integration with lion-field elements.
+ * @desc LionFieldset is basically a 'sub form' and can have its own nested sub forms.
+ * It mimics the native <fieldset> element in this sense, but has all the functionality of
+ * a FormControl (advanced styling, validation, interaction states etc.) Also see
+ * FormGroupMixin it depends on.
+ *
+ * LionFieldset enables the '_isFormOrFieldset' flag in FormRegistrarMixin. This makes .formElements
+ * act not only as an array, but also as an object (see FormRegistarMixin for more information).
+ * As a bonus, It can also group children having names ending with '[]'.
+ *
+ * Above will be  helpful for both forms and sub forms, which can contain sub forms as children
+ * as well and allow for a nested form structure.
+ * Contrary, other form groups (choice groups like radio-group, checkbox-group and (multi)select)
+ * don't: they should be considered 'end nodes' or 'leaves' of the form and their children/formElements
+ * cannot be accessed individually via object keys.
  *
  * @customElement lion-fieldset
  * @extends {LitElement}
  */
-export class LionFieldset extends FormRegistrarMixin(
-  FormControlMixin(ValidateMixin(DisabledMixin(SlotMixin(LitElement)))),
-) {
-  static get properties() {
-    return {
-      name: {
-        type: String,
-      },
-      // TODO: Move property submitted to InteractionStateMixin.
-      submitted: {
-        type: Boolean,
-        reflect: true,
-      },
-      focused: {
-        type: Boolean,
-        reflect: true,
-      },
-      dirty: {
-        type: Boolean,
-        reflect: true,
-      },
-      touched: {
-        type: Boolean,
-        reflect: true,
-      },
-    };
-  }
-
-  get touched() {
-    return this.__touched;
-  }
-
-  set touched(value) {
-    const oldVal = this.__touched;
-    this.__touched = value;
-    this.requestUpdate('touched', oldVal);
-  }
-
-  get _inputNode() {
-    return this;
-  }
-
-  get modelValue() {
-    return this._getFromAllFormElements('modelValue');
-  }
-
-  set modelValue(values) {
-    this._setValueMapForAllFormElements('modelValue', values);
-  }
-
-  get serializedValue() {
-    return this._getFromAllFormElements('serializedValue');
-  }
-
-  set serializedValue(values) {
-    this._setValueMapForAllFormElements('serializedValue', values);
-  }
-
-  get formattedValue() {
-    return this._getFromAllFormElements('formattedValue');
-  }
-
-  set formattedValue(values) {
-    this._setValueMapForAllFormElements('formattedValue', values);
-  }
-
-  get prefilled() {
-    return this._everyFormElementHas('prefilled');
-  }
-
-  get formElementsArray() {
-    return Object.keys(this.formElements).reduce((result, name) => {
-      const element = this.formElements[name];
-      return result.concat(Array.isArray(element) ? element : [element]);
-    }, []);
-  }
-
-  set fieldName(value) {
-    this.__fieldName = value;
-  }
-
-  get fieldName() {
-    const label =
-      this.label ||
-      (this.querySelector('[slot=label]') && this.querySelector('[slot=label]').textContent);
-    return this.__fieldName || label || this.name;
-  }
-
+export class LionFieldset extends FormGroupMixin(LitElement) {
   constructor() {
     super();
-    this.disabled = false;
-    this.submitted = false;
-    this.dirty = false;
-    this.touched = false;
-    this.focused = false;
-    this.formElements = {};
-    this.__addedSubValidators = false;
-
-    this._checkForOutsideClick = this._checkForOutsideClick.bind(this);
-
-    this.addEventListener('focusin', this._syncFocused);
-    this.addEventListener('focusout', this._onFocusOut);
-    this.addEventListener('dirty-changed', this._syncDirty);
-    this.addEventListener('validate-performed', this.__validate);
-
-    this.defaultValidators = [new FormElementsHaveNoError()];
-  }
-
-  connectedCallback() {
-    // eslint-disable-next-line wc/guard-super-call
-    super.connectedCallback();
-    this._setRole();
-  }
-
-  disconnectedCallback() {
-    super.disconnectedCallback(); // eslint-disable-line wc/guard-super-call
-
-    if (this.__hasActiveOutsideClickHandling) {
-      document.removeEventListener('click', this._checkForOutsideClick);
-      this.__hasActiveOutsideClickHandling = false;
-    }
-  }
-
-  updated(changedProps) {
-    super.updated(changedProps);
-
-    if (changedProps.has('disabled')) {
-      if (this.disabled) {
-        this.__requestChildrenToBeDisabled();
-      } else {
-        this.__retractRequestChildrenToBeDisabled();
-      }
-    }
-
-    if (changedProps.has('focused')) {
-      if (this.focused === true) {
-        this.__setupOutsideClickHandling();
-      }
-    }
-  }
-
-  __setupOutsideClickHandling() {
-    if (!this.__hasActiveOutsideClickHandling) {
-      document.addEventListener('click', this._checkForOutsideClick);
-      this.__hasActiveOutsideClickHandling = true;
-    }
-  }
-
-  _checkForOutsideClick(event) {
-    const outsideGroupClicked = !this.contains(event.target);
-    if (outsideGroupClicked) {
-      this.touched = true;
-    }
-  }
-
-  __requestChildrenToBeDisabled() {
-    this.formElementsArray.forEach(child => {
-      if (child.makeRequestToBeDisabled) {
-        child.makeRequestToBeDisabled();
-      }
-    });
-  }
-
-  __retractRequestChildrenToBeDisabled() {
-    this.formElementsArray.forEach(child => {
-      if (child.retractRequestToBeDisabled) {
-        child.retractRequestToBeDisabled();
-      }
-    });
-  }
-
-  // eslint-disable-next-line class-methods-use-this
-  inputGroupTemplate() {
-    return html`
-      <div class="input-group">
-        <slot></slot>
-      </div>
-    `;
-  }
-
-  submitGroup() {
-    this.submitted = true;
-    this.formElementsArray.forEach(child => {
-      if (typeof child.submitGroup === 'function') {
-        child.submitGroup();
-      } else {
-        child.submitted = true; // eslint-disable-line no-param-reassign
-      }
-    });
-  }
-
-  serializeGroup() {
-    const childrenNames = Object.keys(this.formElements);
-    const serializedValues = childrenNames.length > 0 ? {} : undefined;
-    childrenNames.forEach(name => {
-      const element = this.formElements[name];
-      if (Array.isArray(element)) {
-        serializedValues[name] = this.__serializeElements(element);
-      } else {
-        const serializedValue = this.__serializeElement(element);
-        if (serializedValue || serializedValue === 0) {
-          serializedValues[name] = serializedValue;
-        }
-      }
-    });
-    return serializedValues;
-  }
-
-  resetGroup() {
-    this.formElementsArray.forEach(child => {
-      if (typeof child.resetGroup === 'function') {
-        child.resetGroup();
-      } else if (typeof child.reset === 'function') {
-        child.reset();
-      }
-    });
-
-    this.resetInteractionState();
-  }
-
-  resetInteractionState() {
-    this.submitted = false;
-    this.touched = false;
-    this.dirty = false;
-    this.formElementsArray.forEach(formElement => {
-      if (typeof formElement.resetInteractionState === 'function') {
-        formElement.resetInteractionState();
-      }
-    });
-  }
-
-  _getFromAllFormElements(property) {
-    if (!this.formElements) {
-      return undefined;
-    }
-    const childrenNames = Object.keys(this.formElements);
-    const values = {};
-    childrenNames.forEach(name => {
-      if (Array.isArray(this.formElements[name])) {
-        // grouped via myName[]
-        values[name] = this.formElements[name].map(node => node.modelValue);
-      } else {
-        // not grouped
-        values[name] = this.formElements[name][property];
-      }
-    });
-    return values;
-  }
-
-  _setValueForAllFormElements(property, value) {
-    this.formElementsArray.forEach(el => {
-      el[property] = value; // eslint-disable-line no-param-reassign
-    });
-  }
-
-  async _setValueMapForAllFormElements(property, values) {
-    if (!this.__readyForRegistration) {
-      await this.registrationReady;
-    }
-
-    if (values && typeof values === 'object') {
-      Object.keys(values).forEach(name => {
-        if (Array.isArray(this.formElements[name])) {
-          this.formElements[name].forEach((el, index) => {
-            el[property] = values[name][index]; // eslint-disable-line no-param-reassign
-          });
-        }
-        this.formElements[name][property] = values[name];
-      });
-    }
-  }
-
-  _anyFormElementHas(property) {
-    return Object.keys(this.formElements).some(name => {
-      if (Array.isArray(this.formElements[name])) {
-        return this.formElements[name].some(el => !!el[property]);
-      }
-      return !!this.formElements[name][property];
-    });
-  }
-
-  _anyFormElementHasFeedbackFor(state) {
-    return Object.keys(this.formElements).some(name => {
-      if (Array.isArray(this.formElements[name])) {
-        return this.formElements[name].some(el => !!el.hasFeedbackFor.includes(state));
-      }
-      return !!this.formElements[name].hasFeedbackFor.includes(state);
-    });
-  }
-
-  _everyFormElementHas(property) {
-    return Object.keys(this.formElements).every(name => {
-      if (Array.isArray(this.formElements[name])) {
-        return this.formElements[name].every(el => !!el[property]);
-      }
-      return !!this.formElements[name][property];
-    });
-  }
-
-  /**
-   * Gets triggered by event 'validate-performed' which enabled us to handle 2 different situations
-   *   - react on modelValue change, which says something about the validity as a whole
-   *       (at least two checkboxes for instance) and nothing about the children's values
-   *   - children validity states have changed, so fieldset needs to update itself based on that
-   */
-  __validate(ev) {
-    if (ev && this.isRegisteredFormElement(ev.target)) {
-      this.validate();
-    }
-  }
-
-  _syncFocused() {
-    this.focused = this._anyFormElementHas('focused');
-  }
-
-  _onFocusOut(ev) {
-    const lastEl = this.formElementsArray[this.formElementsArray.length - 1];
-    if (ev.target === lastEl) {
-      this.touched = true;
-    }
-    this.focused = false;
-  }
-
-  _syncDirty() {
-    this.dirty = this._anyFormElementHas('dirty');
-  }
-
-  _setRole(role) {
-    this.setAttribute('role', role || 'group');
-  }
-
-  // eslint-disable-next-line class-methods-use-this
-  __serializeElement(element) {
-    if (!element.disabled) {
-      if (typeof element.serializeGroup === 'function') {
-        return element.serializeGroup();
-      }
-      return element.serializedValue;
-    }
-    return undefined;
-  }
-
-  __serializeElements(elements) {
-    const serializedValues = [];
-    elements.forEach(element => {
-      const serializedValue = this.__serializeElement(element);
-      if (serializedValue || serializedValue === 0) {
-        serializedValues.push(serializedValue);
-      }
-    });
-    return serializedValues;
-  }
-
-  /**
-   * Adds the element to an object with the child name as a key
-   * Note: this is different to the default behavior of just beeing an array
-   *
-   * @override
-   */
-  addFormElement(child, indexToInsertAt) {
-    const { name } = child;
-    if (!name) {
-      console.info('Error Node:', child); // eslint-disable-line no-console
-      throw new TypeError('You need to define a name');
-    }
-    if (name === this.name && !this._childrenCanHaveSameName) {
-      console.info('Error Node:', child); // eslint-disable-line no-console
-      throw new TypeError(`You can not have the same name "${name}" as your parent`);
-    }
-
-    if (this.disabled) {
-      // eslint-disable-next-line no-param-reassign
-      child.makeRequestToBeDisabled();
-    }
-
-    if (name.substr(-2) === '[]' || this._childNamesCanBeDuplicate) {
-      if (!Array.isArray(this.formElements[name])) {
-        this.formElements[name] = [];
-      }
-      if (indexToInsertAt > 0) {
-        this.formElements[name].splice(indexToInsertAt, 0, child);
-      } else {
-        this.formElements[name].push(child);
-      }
-    } else if (!this.formElements[name]) {
-      this.formElements[name] = child;
-    } else {
-      console.info('Error Node:', child); // eslint-disable-line no-console
-      throw new TypeError(
-        `Name "${name}" is already registered - if you want an array add [] to the end`,
-      );
-    }
-
-    // This is a way to let the child element (a lion-fieldset or lion-field) know, about its parent
-    // eslint-disable-next-line no-param-reassign
-    child.__parentFormGroup = this;
-
-    // aria-describedby of (nested) children
-
-    // TODO: Teardown in removeFormElement
-
-    let parent = this;
-    while (parent) {
-      this.constructor._addDescriptionElementIdsToField(
-        child,
-        parent._getAriaDescriptionElements(),
-      );
-      // Also check if the newly added child needs to refer grandparents
-      parent = parent.__parentFormGroup;
-    }
-
-    this.validate();
-  }
-
-  // eslint-disable-next-line class-methods-use-this
-  get _childrenCanHaveSameName() {
-    return false;
-  }
-
-  // eslint-disable-next-line class-methods-use-this
-  get _childNamesCanBeDuplicate() {
-    return false;
-  }
-
-  /**
-   * Gathers initial model values of all children. Used
-   * when resetGroup() is called.
-   */
-  get _initialModelValue() {
-    return this._getFromAllFormElements('_initialModelValue');
-  }
-
-  /**
-   * Add aria-describedby to child element(field), so that it points to feedback/help-text of
-   * parent(fieldset)
-   * @param {LionField} field - the child: lion-field/lion-input/lion-textarea
-   * @param {array} descriptionElements  - description elements like feedback and help-text
-   */
-  static _addDescriptionElementIdsToField(field, descriptionElements) {
-    const orderedEls = getAriaElementsInRightDomOrder(descriptionElements, { reverse: true });
-    orderedEls.forEach(el => {
-      if (field.addToAriaDescribedBy) {
-        field.addToAriaDescribedBy(el, { reorder: false });
-      }
-    });
-  }
-
-  removeFormElement(child) {
-    const { name } = child;
-    if (name.substr(-2) === '[]' && this.formElements[name]) {
-      const index = this.formElements[name].indexOf(child);
-      if (index > -1) {
-        this.formElements[name].splice(index, 1);
-      }
-    } else if (this.formElements[name]) {
-      delete this.formElements[name];
-    }
-    this.validate();
+    /** @override from FormRegistrarMixin */
+    this._isFormOrFieldset = true;
   }
 }
diff --git a/packages/fieldset/test/lion-fieldset.test.js b/packages/fieldset/test/lion-fieldset.test.js
index 568c5d569..497ae31b2 100644
--- a/packages/fieldset/test/lion-fieldset.test.js
+++ b/packages/fieldset/test/lion-fieldset.test.js
@@ -1,6 +1,7 @@
 import {
   expect,
   fixture,
+  fixtureSync,
   html,
   unsafeStatic,
   triggerFocusFor,
@@ -39,7 +40,9 @@ beforeEach(() => {
   localizeTearDown();
 });
 
+// TODO: seperate fieldset and FormGroup tests
 describe('<lion-fieldset>', () => {
+  // TODO: Tests below belong to FormControlMixin. Preferably run suite integration test
   it(`has a fieldName based on the label`, async () => {
     const el1 = await fixture(html`<${tag} label="foo">${inputSlots}</${tag}>`);
     expect(el1.fieldName).to.equal(el1._labelNode.textContent);
@@ -60,13 +63,15 @@ describe('<lion-fieldset>', () => {
     expect(el.__fieldName).to.equal(el.fieldName);
   });
 
-  it(`${tagString} has an up to date list of every form element in #formElements`, async () => {
+  // TODO: Tests below belong to FormRegistrarMixin. Preferably run suite integration test
+
+  it(`${tagString} has an up to date list of every form element in .formElements`, async () => {
     const el = await fixture(html`<${tag}>${inputSlots}</${tag}>`);
     await nextFrame();
-    expect(Object.keys(el.formElements).length).to.equal(3);
+    expect(el.formElements.keys().length).to.equal(3);
     expect(el.formElements['hobbies[]'].length).to.equal(2);
     el.removeChild(el.formElements['hobbies[]'][0]);
-    expect(Object.keys(el.formElements).length).to.equal(3);
+    expect(el.formElements.keys().length).to.equal(3);
     expect(el.formElements['hobbies[]'].length).to.equal(1);
   });
 
@@ -79,9 +84,9 @@ describe('<lion-fieldset>', () => {
       </${tag}>
     `);
     await nextFrame();
-    expect(el.formElementsArray.length).to.equal(1);
+    expect(el.formElements.length).to.equal(1);
     el.children[0].removeChild(el.formElements.foo);
-    expect(el.formElementsArray.length).to.equal(0);
+    expect(el.formElements.length).to.equal(0);
   });
 
   it('handles names with ending [] as an array', async () => {
@@ -91,7 +96,7 @@ describe('<lion-fieldset>', () => {
     el.formElements['hobbies[]'][0].modelValue = { checked: false, value: 'chess' };
     el.formElements['hobbies[]'][1].modelValue = { checked: false, value: 'rugby' };
 
-    expect(Object.keys(el.formElements).length).to.equal(3);
+    expect(el.formElements.keys().length).to.equal(3);
     expect(el.formElements['hobbies[]'].length).to.equal(2);
     expect(el.formElements['hobbies[]'][0].modelValue.value).to.equal('chess');
     expect(el.formElements['gender[]'][0].modelValue.value).to.equal('male');
@@ -166,15 +171,17 @@ describe('<lion-fieldset>', () => {
     const el = await fixture(html`<${tag}>${inputSlots}</${tag}>`);
     const newField = await fixture(html`<${childTag} name="lastName"></${childTag}>`);
 
-    expect(Object.keys(el.formElements).length).to.equal(3);
+    expect(el.formElements.keys().length).to.equal(3);
 
     el.appendChild(newField);
-    expect(Object.keys(el.formElements).length).to.equal(4);
+    expect(el.formElements.keys().length).to.equal(4);
 
     el._inputNode.removeChild(newField);
-    expect(Object.keys(el.formElements).length).to.equal(3);
+    expect(el.formElements.keys().length).to.equal(3);
   });
 
+  // TODO: Tests below belong to FormGroupMixin. Preferably run suite integration test
+
   it('can read/write all values (of every input) via this.modelValue', async () => {
     const el = await fixture(html`
       <${tag}>
@@ -231,6 +238,32 @@ describe('<lion-fieldset>', () => {
     expect(el.formElements.lastName.modelValue).to.equal(2);
   });
 
+  it('does not list disabled values in this.modelValue', async () => {
+    const el = await fixture(html`
+      <${tag}>
+        <${childTag} name="a" disabled .modelValue="${'x'}"></${childTag}>
+        <${childTag} name="b" .modelValue="${'x'}"></${childTag}>
+        <${tag} name="newFieldset">
+          <${childTag} name="c" .modelValue="${'x'}"></${childTag}>
+          <${childTag} name="d" disabled .modelValue="${'x'}"></${childTag}>
+        </${tag}>
+        <${tag} name="disabledFieldset" disabled>
+          <${childTag} name="e"  .modelValue="${'x'}"></${childTag}>
+        </${tag}>
+      </${tag}>
+    `);
+    await el.registrationReady;
+    const newFieldset = el.querySelector('lion-fieldset');
+    await newFieldset.registrationReady;
+
+    expect(el.modelValue).to.deep.equal({
+      b: 'x',
+      newFieldset: {
+        c: 'x',
+      },
+    });
+  });
+
   it('does not throw if setter data of this.modelValue can not be handled', async () => {
     const el = await fixture(html`
       <${tag}>
@@ -308,7 +341,7 @@ describe('<lion-fieldset>', () => {
     expect(el.modelValue).to.eql(initialSerializedValue);
   });
 
-  describe('validation', () => {
+  describe('Validation', () => {
     it('validates on init', async () => {
       class IsCat extends Validator {
         constructor() {
@@ -409,7 +442,7 @@ describe('<lion-fieldset>', () => {
     });
   });
 
-  describe('interaction states', () => {
+  describe('Interaction states', () => {
     it('has false states (dirty, touched, prefilled) on init', async () => {
       const fieldset = await fixture(html`<${tag}>${inputSlots}</${tag}>`);
       await nextFrame();
@@ -453,7 +486,7 @@ describe('<lion-fieldset>', () => {
     it('becomes prefilled if all form elements are prefilled', async () => {
       const el = await fixture(html`
         <${tag}>
-          <${childTag} name="input1" prefilled></${childTag}>
+          <${childTag} name="input1" .modelValue="${'prefilled'}"></${childTag}>
           <${childTag} name="input2"></${childTag}>
         </${tag}>
       `);
@@ -462,8 +495,8 @@ describe('<lion-fieldset>', () => {
 
       const el2 = await fixture(html`
         <${tag}>
-          <${childTag} name="input1" prefilled></${childTag}>
-          <${childTag} name="input2" prefilled></${childTag}>
+          <${childTag} name="input1" .modelValue="${'prefilled'}"></${childTag}>
+          <${childTag} name="input2" .modelValue="${'prefilled'}"></${childTag}>
         </${tag}>
       `);
       await nextFrame();
@@ -515,7 +548,7 @@ describe('<lion-fieldset>', () => {
       `);
 
       outside.click();
-      expect(el.touched, 'unfocused fieldset should stays untouched').to.be.false;
+      expect(el.touched, 'unfocused fieldset should stay untouched').to.be.false;
 
       el.children[1].focus();
       el.children[2].focus();
@@ -524,7 +557,6 @@ describe('<lion-fieldset>', () => {
       outside.click(); // blur the group via a click
       outside.focus(); // a real mouse click moves focus as well
       expect(el.touched).to.be.true;
-
       expect(el2.touched).to.be.false;
     });
 
@@ -591,9 +623,30 @@ describe('<lion-fieldset>', () => {
       expect(el.validationStates.error.Input1IsTen).to.be.true;
       expect(el.hasFeedbackFor).to.deep.equal(['error']);
     });
+
+    it.skip('(re)initializes children interaction states on registration ready', async () => {
+      const fieldset = await fixtureSync(html`
+      <${tag} .modelValue="${{ a: '1', b: '2' }}">
+        <${childTag} name="a"></${childTag}>
+        <${childTag} name="b"></${childTag}>
+      </${tag}>`);
+      const childA = fieldset.querySelector('[name="a"]');
+      const childB = fieldset.querySelector('[name="b"]');
+      const spyA = sinon.spy(childA, 'initInteractionState');
+      const spyB = sinon.spy(childB, 'initInteractionState');
+      expect(fieldset.prefilled).to.be.false;
+      expect(fieldset.dirty).to.be.false;
+      await fieldset.registrationReady;
+      await nextFrame();
+      expect(spyA).to.have.been.called;
+      expect(spyB).to.have.been.called;
+      expect(fieldset.prefilled).to.be.true;
+      expect(fieldset.dirty).to.be.false;
+    });
   });
 
-  describe('serialize', () => {
+  // TODO: this should be tested in FormGroupMixin
+  describe('serializedValue', () => {
     it('use form elements serializedValue', async () => {
       const fieldset = await fixture(html`<${tag}>${inputSlots}</${tag}>`);
       await nextFrame();
@@ -604,7 +657,7 @@ describe('<lion-fieldset>', () => {
       fieldset.formElements['gender[]'][1].modelValue = { checked: false, value: 'female' };
       fieldset.formElements.color.modelValue = { checked: false, value: 'blue' };
       expect(fieldset.formElements['hobbies[]'][0].serializedValue).to.equal('Bar-serialized');
-      expect(fieldset.serializeGroup()).to.deep.equal({
+      expect(fieldset.serializedValue).to.deep.equal({
         'hobbies[]': ['Bar-serialized', { checked: false, value: 'rugby' }],
         'gender[]': [
           { checked: false, value: 'male' },
@@ -614,6 +667,27 @@ describe('<lion-fieldset>', () => {
       });
     });
 
+    it('treats names with ending [] as arrays', async () => {
+      const fieldset = await fixture(html`<${tag}>${inputSlots}</${tag}>`);
+      await nextFrame();
+      fieldset.formElements['hobbies[]'][0].modelValue = { checked: false, value: 'chess' };
+      fieldset.formElements['hobbies[]'][1].modelValue = { checked: false, value: 'rugby' };
+      fieldset.formElements['gender[]'][0].modelValue = { checked: false, value: 'male' };
+      fieldset.formElements['gender[]'][1].modelValue = { checked: false, value: 'female' };
+      fieldset.formElements.color.modelValue = { checked: false, value: 'blue' };
+      expect(fieldset.serializedValue).to.deep.equal({
+        'hobbies[]': [
+          { checked: false, value: 'chess' },
+          { checked: false, value: 'rugby' },
+        ],
+        'gender[]': [
+          { checked: false, value: 'male' },
+          { checked: false, value: 'female' },
+        ],
+        color: { checked: false, value: 'blue' },
+      });
+    });
+
     it('0 is a valid value to be serialized', async () => {
       const fieldset = await fixture(html`
       <${tag}>
@@ -621,48 +695,22 @@ describe('<lion-fieldset>', () => {
       </${tag}>`);
       await nextFrame();
       fieldset.formElements.price.modelValue = 0;
-      expect(fieldset.serializeGroup()).to.deep.equal({ price: 0 });
+      expect(fieldset.serializedValue).to.deep.equal({ price: 0 });
     });
 
-    it('__serializeElements serializes 0 as a valid value', async () => {
-      const fieldset = await fixture(html`<${tag}></${tag}>`);
+    it.skip('serializes undefined values as ""(nb radios/checkboxes are always serialized)', async () => {
+      const fieldset = await fixture(html`
+        <${tag}>
+          <${childTag} name="custom[]"></${childTag}>
+          <${childTag} name="custom[]"></${childTag}>
+        </${tag}>
+      `);
       await nextFrame();
-      const elements = [{ serializedValue: 0 }];
-      expect(fieldset.__serializeElements(elements)).to.deep.equal([0]);
-    });
+      fieldset.formElements['custom[]'][0].modelValue = 'custom 1';
+      fieldset.formElements['custom[]'][1].modelValue = undefined;
 
-    it('form elements which are not disabled', async () => {
-      const fieldset = await fixture(html`<${tag}>${inputSlots}</${tag}>`);
-      await nextFrame();
-      fieldset.formElements.color.modelValue = { checked: false, value: 'blue' };
-      fieldset.formElements['hobbies[]'][0].modelValue = { checked: true, value: 'football' };
-      fieldset.formElements['gender[]'][0].modelValue = { checked: true, value: 'male' };
-      fieldset.formElements['hobbies[]'][1].modelValue = { checked: false, value: 'rugby' };
-      fieldset.formElements['gender[]'][1].modelValue = { checked: false, value: 'female' };
-      fieldset.formElements.color.modelValue = { checked: false, value: 'blue' };
-
-      expect(fieldset.serializeGroup()).to.deep.equal({
-        'hobbies[]': [
-          { checked: true, value: 'football' },
-          { checked: false, value: 'rugby' },
-        ],
-        'gender[]': [
-          { checked: true, value: 'male' },
-          { checked: false, value: 'female' },
-        ],
-        color: { checked: false, value: 'blue' },
-      });
-      fieldset.formElements.color.disabled = true;
-
-      expect(fieldset.serializeGroup()).to.deep.equal({
-        'hobbies[]': [
-          { checked: true, value: 'football' },
-          { checked: false, value: 'rugby' },
-        ],
-        'gender[]': [
-          { checked: true, value: 'male' },
-          { checked: false, value: 'female' },
-        ],
+      expect(fieldset.serializedValue).to.deep.equal({
+        'custom[]': ['custom 1', ''],
       });
     });
 
@@ -681,9 +729,9 @@ describe('<lion-fieldset>', () => {
       newFieldset.formElements['gender[]'][1].modelValue = { checked: false, value: 'female' };
       newFieldset.formElements.color.modelValue = { checked: false, value: 'blue' };
       fieldset.formElements.comment.modelValue = 'Foo';
-      expect(Object.keys(fieldset.formElements).length).to.equal(2);
-      expect(Object.keys(newFieldset.formElements).length).to.equal(3);
-      expect(fieldset.serializeGroup()).to.deep.equal({
+      expect(fieldset.formElements.keys().length).to.equal(2);
+      expect(newFieldset.formElements.keys().length).to.equal(3);
+      expect(fieldset.serializedValue).to.deep.equal({
         comment: 'Foo',
         newfieldset: {
           'hobbies[]': [
@@ -699,7 +747,23 @@ describe('<lion-fieldset>', () => {
       });
     });
 
-    it('will exclude form elements within an disabled fieldset', async () => {
+    it('does not serialize disabled values', async () => {
+      const fieldset = await fixture(html`
+        <${tag}>
+          <${childTag} name="custom[]"></${childTag}>
+          <${childTag} name="custom[]"></${childTag}>
+        </${tag}>
+      `);
+      await nextFrame();
+      fieldset.formElements['custom[]'][0].modelValue = 'custom 1';
+      fieldset.formElements['custom[]'][1].disabled = true;
+
+      expect(fieldset.serializedValue).to.deep.equal({
+        'custom[]': ['custom 1'],
+      });
+    });
+
+    it('will exclude form elements within a disabled fieldset', async () => {
       const fieldset = await fixture(html`
         <${tag} name="userData">
           <${childTag} name="comment"></${childTag}>
@@ -717,7 +781,7 @@ describe('<lion-fieldset>', () => {
       newFieldset.formElements.color.modelValue = { checked: false, value: 'blue' };
       newFieldset.formElements.color.disabled = true;
 
-      expect(fieldset.serializeGroup()).to.deep.equal({
+      expect(fieldset.serializedValue).to.deep.equal({
         comment: 'Foo',
         newfieldset: {
           'hobbies[]': [
@@ -732,7 +796,7 @@ describe('<lion-fieldset>', () => {
       });
 
       newFieldset.formElements.color.disabled = false;
-      expect(fieldset.serializeGroup()).to.deep.equal({
+      expect(fieldset.serializedValue).to.deep.equal({
         comment: 'Foo',
         newfieldset: {
           'hobbies[]': [
@@ -747,43 +811,6 @@ describe('<lion-fieldset>', () => {
         },
       });
     });
-
-    it('treats names with ending [] as arrays', async () => {
-      const fieldset = await fixture(html`<${tag}>${inputSlots}</${tag}>`);
-      await nextFrame();
-      fieldset.formElements['hobbies[]'][0].modelValue = { checked: false, value: 'chess' };
-      fieldset.formElements['hobbies[]'][1].modelValue = { checked: false, value: 'rugby' };
-      fieldset.formElements['gender[]'][0].modelValue = { checked: false, value: 'male' };
-      fieldset.formElements['gender[]'][1].modelValue = { checked: false, value: 'female' };
-      fieldset.formElements.color.modelValue = { checked: false, value: 'blue' };
-      expect(fieldset.serializeGroup()).to.deep.equal({
-        'hobbies[]': [
-          { checked: false, value: 'chess' },
-          { checked: false, value: 'rugby' },
-        ],
-        'gender[]': [
-          { checked: false, value: 'male' },
-          { checked: false, value: 'female' },
-        ],
-        color: { checked: false, value: 'blue' },
-      });
-    });
-
-    it('does not serialize undefined values (nb radios/checkboxes are always serialized)', async () => {
-      const fieldset = await fixture(html`
-        <${tag}>
-          <${childTag} name="custom[]"></${childTag}>
-          <${childTag} name="custom[]"></${childTag}>
-        </${tag}>
-      `);
-      await nextFrame();
-      fieldset.formElements['custom[]'][0].modelValue = 'custom 1';
-      fieldset.formElements['custom[]'][1].modelValue = undefined;
-
-      expect(fieldset.serializeGroup()).to.deep.equal({
-        'custom[]': ['custom 1'],
-      });
-    });
   });
 
   describe('Reset', () => {
@@ -883,7 +910,7 @@ describe('<lion-fieldset>', () => {
       fieldset.submitted = true;
       fieldset.resetGroup();
       expect(fieldset.submitted).to.equal(false);
-      fieldset.formElementsArray.forEach(el => {
+      fieldset.formElements.forEach(el => {
         expect(el.submitted).to.equal(false);
       });
     });
diff --git a/packages/form-system/test/form-integrations.test.js b/packages/form-system/test/form-integrations.test.js
new file mode 100644
index 000000000..602cf16ba
--- /dev/null
+++ b/packages/form-system/test/form-integrations.test.js
@@ -0,0 +1,33 @@
+import { expect, fixture, html } from '@open-wc/testing';
+import './helpers/umbrella-form.js';
+
+// Test umbrella form
+describe('Form Integrations', () => {
+  it.skip('".serializedValue" returns all non disabled fields based on form structure', async () => {
+    const el = await fixture(
+      html`
+        <umbrella-form></umbrella-form>
+      `,
+    );
+    const formEl = el._lionFormNode;
+    expect(formEl.serializedValue).to.eql({
+      bio: '',
+      'checkers[]': [[]],
+      comments: '',
+      date: '2000-12-12',
+      datepicker: '2020-12-12',
+      dinosaurs: '',
+      email: '',
+      favoriteColor: 'hotpink',
+      full_name: {
+        first_name: '',
+        last_name: '',
+      },
+      iban: '',
+      lyrics: '1',
+      money: '',
+      range: 2.3,
+      terms: [],
+    });
+  });
+});
diff --git a/packages/form-system/test/helpers/umbrella-form.js b/packages/form-system/test/helpers/umbrella-form.js
new file mode 100644
index 000000000..35d1eedb4
--- /dev/null
+++ b/packages/form-system/test/helpers/umbrella-form.js
@@ -0,0 +1,106 @@
+import { LitElement, html } from '@lion/core';
+import { Required, MinLength } from '@lion/validate';
+
+export class UmbrellaForm extends LitElement {
+  get _lionFormNode() {
+    return this.shadowRoot.querySelector('lion-form');
+  }
+
+  render() {
+    return html`
+      <lion-form>
+        <form>
+          <lion-fieldset name="full_name">
+            <lion-input
+              name="first_name"
+              label="First Name"
+              .validators="${[new Required()]}"
+            ></lion-input>
+            <lion-input
+              name="last_name"
+              label="Last Name"
+              .validators="${[new Required()]}"
+            ></lion-input>
+          </lion-fieldset>
+          <lion-input-date
+            name="date"
+            label="Date of application"
+            .modelValue="${new Date('2000-12-12')}"
+            .validators="${[new Required()]}"
+          ></lion-input-date>
+          <lion-input-datepicker
+            name="datepicker"
+            label="Date to be picked"
+            .modelValue="${new Date('2020-12-12')}"
+            .validators="${[new Required()]}"
+          ></lion-input-datepicker>
+          <lion-textarea
+            name="bio"
+            label="Biography"
+            .validators="${[new Required(), new MinLength(10)]}"
+            help-text="Please enter at least 10 characters"
+          ></lion-textarea>
+          <lion-input-amount name="money" label="Money"></lion-input-amount>
+          <lion-input-iban name="iban" label="Iban"></lion-input-iban>
+          <lion-input-email name="email" label="Email"></lion-input-email>
+          <lion-checkbox-group
+            label="What do you like?"
+            name="checkers[]"
+            .validators="${[new Required()]}"
+          >
+            <lion-checkbox .choiceValue=${'foo'} label="I like foo"></lion-checkbox>
+            <lion-checkbox .choiceValue=${'bar'} label="I like bar"></lion-checkbox>
+            <lion-checkbox .choiceValue=${'baz'} label="I like baz"></lion-checkbox>
+          </lion-checkbox-group>
+          <lion-radio-group
+            name="dinosaurs"
+            label="Favorite dinosaur"
+            .validators="${[new Required()]}"
+          >
+            <lion-radio .choiceValue=${'allosaurus'} label="allosaurus"></lion-radio>
+            <lion-radio .choiceValue=${'brontosaurus'} label="brontosaurus"></lion-radio>
+            <lion-radio .choiceValue=${'diplodocus'} label="diplodocus"></lion-radio>
+          </lion-radio-group>
+          <lion-select-rich name="favoriteColor" label="Favorite color">
+            <lion-options slot="input">
+              <lion-option .choiceValue=${'red'}>Red</lion-option>
+              <lion-option .choiceValue=${'hotpink'} checked>Hotpink</lion-option>
+              <lion-option .choiceValue=${'teal'}>Teal</lion-option>
+            </lion-options>
+          </lion-select-rich>
+          <lion-select label="Lyrics" name="lyrics" .validators="${[new Required()]}">
+            <select slot="input">
+              <option value="1">Fire up that loud</option>
+              <option value="2">Another round of shots...</option>
+              <option value="3">Drop down for what?</option>
+            </select>
+          </lion-select>
+          <lion-input-range
+            name="range"
+            min="1"
+            max="5"
+            .modelValue="${2.3}"
+            unit="%"
+            step="0.1"
+            label="Input range"
+          ></lion-input-range>
+          <lion-checkbox-group name="terms" .validators="${[new Required()]}">
+            <lion-checkbox label="I blindly accept all terms and conditions"></lion-checkbox>
+          </lion-checkbox-group>
+          <lion-textarea name="comments" label="Comments"></lion-textarea>
+          <div class="buttons">
+            <lion-button raised>Submit</lion-button>
+            <lion-button
+              type="button"
+              raised
+              @click=${ev =>
+                ev.currentTarget.parentElement.parentElement.parentElement.resetGroup()}
+              >Reset</lion-button
+            >
+          </div>
+        </form>
+      </lion-form>
+    `;
+  }
+}
+customElements.define('umbrella-form', UmbrellaForm);
diff --git a/packages/radio-group/src/LionRadioGroup.js b/packages/radio-group/src/LionRadioGroup.js
index 080441e57..2417b2ea0 100644
--- a/packages/radio-group/src/LionRadioGroup.js
+++ b/packages/radio-group/src/LionRadioGroup.js
@@ -1,15 +1,16 @@
+import { LitElement } from '@lion/core';
 import { ChoiceGroupMixin } from '@lion/choice-input';
-import { LionFieldset } from '@lion/fieldset';
+import { FormGroupMixin } from '@lion/fieldset';
 
 /**
  * A wrapper around multiple radios.
  *
  * @extends {LionFieldset}
  */
-export class LionRadioGroup extends ChoiceGroupMixin(LionFieldset) {
+export class LionRadioGroup extends ChoiceGroupMixin(FormGroupMixin(LitElement)) {
   connectedCallback() {
     // eslint-disable-next-line wc/guard-super-call
     super.connectedCallback();
-    this._setRole('radiogroup');
+    this.setAttribute('role', 'radiogroup');
   }
 }
diff --git a/packages/radio-group/test/lion-radio-group.test.js b/packages/radio-group/test/lion-radio-group.test.js
index ddc835977..621e6f50c 100644
--- a/packages/radio-group/test/lion-radio-group.test.js
+++ b/packages/radio-group/test/lion-radio-group.test.js
@@ -37,9 +37,9 @@ describe('<lion-radio-group>', () => {
       </lion-radio-group>
     `);
     await nextFrame();
-    const male = el.formElementsArray[0];
+    const male = el.formElements[0];
     const maleInput = male.querySelector('input');
-    const female = el.formElementsArray[1];
+    const female = el.formElements[1];
     const femaleInput = female.querySelector('input');
 
     expect(male.checked).to.equal(false);
diff --git a/packages/select-rich/src/LionSelectRich.js b/packages/select-rich/src/LionSelectRich.js
index d2f3bf120..22dbdda67 100644
--- a/packages/select-rich/src/LionSelectRich.js
+++ b/packages/select-rich/src/LionSelectRich.js
@@ -1,7 +1,7 @@
 import { ChoiceGroupMixin } from '@lion/choice-input';
 import { css, html, LitElement, SlotMixin } from '@lion/core';
 import { FormControlMixin, FormRegistrarMixin, InteractionStateMixin } from '@lion/field';
-import { formRegistrarManager } from '@lion/field/src/formRegistrarManager.js';
+import { formRegistrarManager } from '@lion/field/src/registration/formRegistrarManager.js';
 import { OverlayMixin, withDropdownConfig } from '@lion/overlays';
 import { ValidateMixin } from '@lion/validate';
 import '../lion-select-invoker.js';
@@ -132,6 +132,11 @@ export class LionSelectRich extends ChoiceGroupMixin(
     this.requestUpdate('modelValue');
   }
 
+  // TODO: quick and dirty fix. Should be possible to do it nicer on a higher layer
+  get serializedValue() {
+    return this.modelValue;
+  }
+
   get checkedIndex() {
     let checkedIndex = -1;
     this.formElements.forEach((option, i) => {
diff --git a/packages/select-rich/test/lion-select-rich.test.js b/packages/select-rich/test/lion-select-rich.test.js
index 296b2e515..5704db4c1 100644
--- a/packages/select-rich/test/lion-select-rich.test.js
+++ b/packages/select-rich/test/lion-select-rich.test.js
@@ -41,15 +41,15 @@ describe('lion-select-rich', () => {
     `);
     await nextFrame();
 
-    expect(el.formElementsArray[0].name).to.equal('foo');
-    expect(el.formElementsArray[1].name).to.equal('foo');
+    expect(el.formElements[0].name).to.equal('foo');
+    expect(el.formElements[1].name).to.equal('foo');
 
     const validChild = await fixture(html`
       <lion-option .choiceValue=${30}>Item 3</lion-option>
     `);
     el.appendChild(validChild);
 
-    expect(el.formElementsArray[2].name).to.equal('foo');
+    expect(el.formElements[2].name).to.equal('foo');
   });
 
   it('throws if a child element without a modelValue like { value: "foo", checked: false } tries to register', async () => {
@@ -108,7 +108,7 @@ describe('lion-select-rich', () => {
     `);
 
     expect(el.modelValue).to.equal('other');
-    expect(el.formElementsArray[2].checked).to.be.true;
+    expect(el.formElements[2].checked).to.be.true;
   });
 
   it(`has a fieldName based on the label`, async () => {