Theres already a game like that, it's called Postal 2. You run around doing nothing and when ever you want you can just pull out a gun and shoot people, that and GTA III. That kind of interactivity was tried with that "awesome" PC FPS, Jurassic Park: Forgot the Subtitle. You were able to twist and manipulate your arm in real time and it had a very impressive physics engine. But the game bit ass. That was not Jurassic Park, that was Trespasser. I actually owned that game once. Yeah that's it. But its based on the Jurassic Park world. Dreamworks made that train wreck of a game.