I want (I play CoD 4 on a console, not answering why or whatever.)

-Interactive Environments. If I blow a hole in the wall with an RPG or C4, I expect to be rewarded with a hiding coward to kill.

-Mountable LMGs/Snipers (Bipod unlocks, and of course improved greatly on what Treyarch did with it)

-Leaning (for console versions) Kinda pushing the idea here.. perhaps the game could detect where you are and let you lean if you're just facing the wall and are near the edge of it.

-Button combinations, I'm thinking instead of sprint cancel, mb if x is pressed while sprinting you slide to the nearest wall or cover, of course there might be a reload fumble or failure with this, but it could be cool.

-Slow motion for SP, cheats for private matches.