MW2 has totally turned me against killstreaks, and for this reason i think it would be kinda cool (maybe not for the entire game but for a certain game type) if instead of killstreaks you got attatchments. in the story mode, you often get weapons with sights, silencers and 203's..so why not in multiplayer? there could be a be a gametype which is a bit like a bare bones playlist, where you have no attatchments or perks, and by getting kills you get an attatchment and a perk, the higher killstreak the higher addition to your kit. you could also have it so that the player has to choose whether they want an attatchment for their weapon system or a perk..for example
3 kills - red dot sight/steady aim
5 kills - silencer/sleight of hand
7 kills - 203/stopping power
it might just be me who thinks this would be good but i dunno..tell me what you think