Whenever I watch something to do with the terminator (never watched the new movies, third one wasnt too great and never bothered with anything after that.) I keep thinking that all the ingredients for a really good videogame are there.
First of all, it would be a really interesting damage model to use.. something really advanced could be done with this for when a terminator gets damaged. Only stuff that would destroy human flesh should cause the robot underneath to become appearant though.. from bullets just bits and pieces could be revealed. When damaged, some improvised repairs could be made. You start with nothing and need to obtain weapons and clothes.
When getting really damaged, it could also become impossible to blend in once its clear to see you are not human.
For the game it could be about more than assasinating people though.. something greater could be at work here and assasinations could only be a part of it. You'd need to look through various sources of info to find the target.
For multiplayer, each player could be their own terminator. There could be various ways to modify yourself with different abilities, but there would be a limit to it.. you'd get a set amount of points to assign. New powers could be unlocked through play, but the amount of points to spend should stay the same for balance reasons.. simply providing more options to someone who unlocks everything without becomeing overpowered.
But there could also be special gamemodes where one player is the terminator, and everyone else is human. Maybe more than one terminator, could depend on the amount of players for balance reasons.
For this mode, one player would be the assasination target but they wouldnt know which one of them. The one thats the target could be locked on by the terminator(s), seeing the target on the radar at all times. The humans would need to work together to take down the terminators.
Mostly regular weapons could be used for this.. pistols, rifles, snipers, shotguns, etc. They would need to be found at the usual places.
But it doesnt end here.. aside from the players, there are also civilians on the selected map.. the maps could usually be a city district, a town or other larger region. And there would also be an active police force that will act accordingly and serves as a third party. Human or terminator, if you are quite openly robbing a gunstore, the police will come after you.
So basicly each player would have two multiplayer characters.. a human and a terminator.
All physical features could be customised just the same since both look human. For terminators whats underneath could differ in appearance based on their upgrades.