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't sending its data to the form).

Once form registration is in place you'll be able to create component libraries that should truly work no matter the environment or libraries being used alongside them (as long as you have an up to date browser).