[TheCoreh]

This is all already possible with current HTML, except for the namespace stuff (Which is too verbose, and was ditched after the failed XHTML effort, since it never really caught on anyway).

You can already create your own custom HTML tags with the `document.registerElement()` API. And then use all the semantic elements you want. You can even add custom rendering and logic to then via the shadow DOM.

There's a lot of existing elements you can already use: http://customelements.io

Browser support is not 100% there yet, but http://polymer-project.org provides a polyfill that works on IE9+.