It's a nice touch on the idea..but just think about FFA or CTF servers. What you will end up having is this:
1)you're fighting with some guys, and having a heated battle and suddenly everything slows down...screwing up your battle...
2)there is one little guy sitting in a corner where no one is constantly switches on force speed....just to piss people off and make the game slow.
that's why I dont' see that reason very viable..