Well considering this is pretty much all I play when it comes to Black Ops and I've written a strategy guide of my own on this gem of a game, I feel inclined to comment here
1. Give the option to allow or disallow stealing of lives. I personally don't mind when it happens, but a lot of players would prefer to have weaker players sit out a round (or 90 seconds) while the rest of the team mops up the mess the other player left behind.
2. Like others have stated, I think Solo leaderboards should be added. It gives a better idea of who is actually a good player and who gets their asses carried to the higher rounds.
3. Fix the game crashing glitches (ie bird+flamethrower in high rounds, carrying a tank over a portal, G-Spawn, etc)