I've always wanted to see a Terminator social stealth game, like Hitman with a T-1000. It would be easier to make it in the future timeline, since a T-1000 can't just take on everyone, but if you wanted to go for the past timeline, you could make a fairly interesting 3 player game. One plays as the Skynet target and has certain objectives to do in the level, like doing their job or buying groceries or enjoying the entertainment (depends on the level), but has to blend in as an A.I. in the level, play the part to hide. The T-800 and T-1000 both need to locate him in secret while also blending in and looking out for each other, one to kill him, preferably secret, and the other to intervene and give the target a chance to escape.