Extending builtin elements not supported

[AndyOGo]

Are you reporting a bug or a feature?

• Bug
• Feature

Expected Behavior

The CustomElementRegistry.define() API specifies the ability to extend builtin elements.
So it should be working as specified.

Actual Behavior

Extending builtin elements isn't fully supported by:

• not all browsers support it and safari even refuses to implement it 😨

  Note: Only Chrome 67 supports customized built-in elements (status) right now. Edge and Firefox will implement it, but Safari has chosen not to implement it. This is unfortunate for accessibility and progressive enhancement. If you think extending native HTML elements is useful, voice your thoughts on 509 and 662 on Github.

• Element Behaviors, and the has="" attribute. A useful alternative to Custom Elements in many cases! WICG/webcomponents#727
• the polyfill does not implement it https://github.com/webcomponents/custom-elements/issues/13

Steps to Reproduce the Problem

Currently we face this issue especially with tables #546 but it's also kinda existing with <axa-button>

[LucaMele]

mmmm https://github.com/WebReflection/built-in-element#built-in-element