My first suggestion is to input an experience bar at either the bottom of your hud or in game when you press start. Just a basic yellow bar that goes across the screen when ever you get xp. Basically the same experience bar that was implemented into MW2. That I liked and would like to see back into the game.
The second sounds better for the more elite players. The ones that can actually get MOAB's. The thing is a kill streak counter that is like below your killstreak window on the bottom right of the screen. Maybe just a plain like number counter. Nothing too fancy to add to the game.
These twos things I would like to see and I know my friends would like to see them as well.. Thanks if you do read this and I hope to see these things implemented into the game in the future.
Oh yeah... As I'm playing and notice a C4 fly across the screen and blow up in my face. It reminded of something.. If you could please touch up the C4 throwing and exploding part.. IRL I don't think people would be chucking C4 around and pulling the trigger randomly.. Maybe if you had to have the C4 land before you are able to explode it. That would be nice to add as well.