Maybe this has been talked about before, maybe it hasn't and I'm a genius. If you've seen the movie The Jackal, with Bruce Willis, you know that it was the gun he was using that made the movie so great. What about making some sort of gun on a tripod controlled by the player in a different location? It would'nt have to be too special, just an M2 and some what to controll it from a "laptop." Or someone could try to recreate the exact thing. If I remember correctly the gun in the movie was one of the guns used on a ZSU (a shilka).
Just an Idea, But if anyone could do it it would be awesome.