I think what'd I'd really like in an MW game is 3028-3050 (as with MW2:M) but with some of the later civil war technology in it (X-Pulse, f**king GIANT VULCAN AC2s, etc).
And I might come under flak for this, but I thought the purple plasma, how lasers worked and the stupid hot lava spammer mech in the console games was "rule of cool"* enough... (What?! I played MW2M/MW3/MW4 long before the console ports!!!!)
Just imagine having that thing stomping towards you and your forces panic; everything from flying dustbins with autocannons, 25-ton stick figures and human/reverse-legged missile boats all falling apart and catching fire because volcanoes ARE hot, some Raven desperado fires a NARC beacon before dying, next thing you know a friendly Annihilator turns the corner at the next city block and shreds it apart with quad uAC20 or whatever else comes better...
KABOOM ONE SHOT ONE KNOCK DOWN ONE KILL
(*lack of a better word so just throw something familiar into that sentence, meh)
Okay I guess I'm getting carried away now. XD