I can only keep repeating myself: separate /usr is not a benefit in itself. If you want to do that to mount it read-only, then you are simply aiming too low, and you should rather work on making / read-only. And you know what? We actually have been working hard on fixing the remaining problems to make this possible. And even enable it by default one of those days.
My recommendation: try to investigate how things really are, and think about them for a while. And then make a smart comment, instead of just calling us idiots. Thank you.