Hell, I'd be happy if browsers sent a content and platform dimensions headers... so that I at least know the screen size, and if it's in a window, the content size that will be filled.... would make it really nice to be able to do adaptive rendering of the markup.
Even removing"Mozilla/" could break UA detection that uses hardcoded string indexes to version numberz. :(
Opera since 9.0 up to 12.x had user-agent without Mozilla. I still use Opera 12.17 and mostly only Google's sites are broken.
Don't get me wrong, I am not advocating UA strings - but to get rid of them, there needs to be an approach where there isn't a punishment for following the rules.