Oooh, lots of great ideas already. I think the combat in ME3 is pretty darn good already, but as some have mentioned there can be some additions.
-Smarter AI. Except for maybe the Phantom, who is very aggressive in the SP, most of the AI kinda stay put. I was playing Wolfenstein New Order awhile back, and Man do those AI's come after. I mean, they will track you down around the corner; behind a box. Although there weren't alot of boxes, iirc. You just had to find cover where you could, but you better not stay long. Friggin Nazhies! Nazhies everywhere!
-When I was buying weapons, I had a hard time cuz I never saw any stats on them. I didn't know what I was buying. Idk, if I missed something there?
-The heavy melee move is too long, imo. I think someone mentioned this. I would like that to be shorter and not so slo-mo. I don't need all that slo mo stuff. (Annnnd a choice of heavy melee weapons would be nice.).
-Some more melee moves. Some melee takedowns.
-Not so many actions on one button? Sometimes I want to crouch, but instead I go vaulting over the friggin box. Right to my death....(lol!, but not funny...lol.)
--Combat is pretty solid, but I would like to see it opened up more. The terrain of battle opened up.
--Oh! And someone mentioned being able to set up tactics for your squad--as much as possible--like the DA series. I would absolutely Love that!