The similarity to "Assass." makes it ideal. As I said in chat, I don't think that it's really a problem that traitor is seen on screen. I think it makes it challenging all around. The traitor can also see his victims/teammates on screen also. Not to mention that the team has it's hands full defending itself against the other team. What's even BETTER is that, although each team has a new "enemy within," the traitor DOESN'T have new allies on the other team b/c THEY don't know who the traitor on the other team is either! And they don't see the reticulation, so they keep shooting at someone who is, ultimately, on their side. What you end up having is fatal confusion and mass paranoia and brilliant opportunities for friendly fire!!! Trust me, in actual play, it's a rush!
The main thing is that the traitor HAS TO START (the first five minutes of the game) secretly. That way, psychologically, the tension builds as people wonder who it's going to be!
If you don't have time to accomplish this, Monoman, maybe I could try, but I really have no idea where to start with something like this.
-- "My kingdom for a Humvee."