Simple class property for all ui elements?

Could we get a class property for all elements that would easily allow us to target a particular element with a class name? So, for one button I could set the class to 'importantButton' and then just target that class in a template node or something?

I can't think of an easy way to do this apart from adding a specific class option to every widget in existence. This would then break when we eventually get to allowing users to have repeated widgets (like subflows but for ui) - as they would then be copies and not individual nodes again.