I stopped playing the game a long time ago. I found it stupid. Anyway, heres my idea:
A first person shooter which returns to the run and gun play style I miss so much. And everything, e-v-e-r-y-t-h-i-n-g would be both interact-able and destructible. Blow up a house, pick up a 2x4 and beat enemies senseless with it.
It would just be crazy, over-the-top action. Like shooting out a window, picking up a shard of glass, throw it throwing-knife-style into a hose hanging from a gas tank, then blow the whole thing sky-high. Stuff like that. Repelling down a dam dual-wielding SMGs.
Plot would involve gov't conspiracy, just so you can fight soldiers instead of weak-ass terrorist or aliens, and maybe limited RPG elements (choose to make yourself sprint faster, use melee better, or the like. Simple stuff).