In Black Ops I noticed that it was too easy to acquire powerful killstreaks (Chopper Gunner, Dogs) by posting up somewhere and killing people who are focussed on the objective (as they should be). And they could then easily control the game with these killstreaks.
I thought of a possible solution to this, so that playing the objective is more productive for an overall win than 'killwhoring' since your killstreaks aren't as easy to come by throughout the whole game.
Every time you earn a killstreak reward, you will need to reach a higher killstreak in a subsequent life to get the same reward. For example if xX MLG L33ts4uzE Xx gets a killstreak of 8 and dies, his Blackbird next time will require a 10 killstreak or something... I thought a good way to scale it might be:
Killstreak of 3 to 7: Increase by 1 to get it the next time around
Killstreak of 8+: Increase by 2 to get it the next time around
This would make killstreaks less of a determining factor in the outcome of an objective gamemode. Obviously, they'd still help.. but they wouldn't completely control the battle and there'd be a bit more incentive to capture flags since you might not have enough time to get a second set of high end killstreaks.