I think a Killzone 3 type warzone game mode would work great on Crysis 2's maps. If the objectives were to switch between 'Team instant Action', 'Crash site' and 'Relay'; it would be friggin awesome. Tbh it wouldn't exactly be hard to implement an assassination type objective, but on maps like Skyline it would be incredibly easy to find them (unless the marker was more of a 'marco polo' type thing, where it only came up on radar every 5-10 seconds as a short blip).
I don't think there's any point putting Power Struggle in Crysis 2. If it came out, I would definitely buy it, but I don't think the long games would be popular enough outside of clan battles, so it'd be difficult to get in a game at all.
Domination is cool, but it's got nothing on Warzone