The whole reason we play this game over other FPS shooters is because of the dynamic that the Nano-Suit brings, if we wanted to play a game without Nano-Suits we'd play Call of Duty, Battlefield, or whatever else is out there.
Pro on the other hand adds an element that this game does need, fewer bullet kills. Sometimes it gets frustrating when you unload a whole clip into someone only for them to get away or worse - turn and kill you while you're reloading / switching weapons. It would be nice to be able to play Pro when you don't feel like unloading half a clip for every kill.
Also there is no reason to have both map packs separate from the normal set. At least merge the Retaliation map pack once Decimation comes out...
I like the idea of an Onslaught type game mode, but I think its a mistake to remove Team IA only mode from the expansions.