Earlier quoted context omitted.
Form registration for webcomponents is coming. Personally when trying to create a component system it's been the number one blocker I've had. Your work arounds were not great - either you'd have to mirror an input in the lightdom (not good if you're using a library that strictly enforces a vdom), or you have to use a forked form component (not good as few people will know to use it and will wonder why the x-input isn…
Can you link me to a page describing this new functionality in action?
As well as the implementation status in chromium: https://www.chromestatus.com/features/4708990554472448