Except police and navy in their house space, Rheinalnd Military and Liberty Navy in Hudson and Bering, and Gallic Royal Navy in Orkney, Tau23, Tau31, and Leeds.
I doubt Leeds would be a good choice.
Other than that... actually, I like that idea. With some time limit (20-60 mins), otherwise people will get bored fast and won't have a single reason to stay alive and try hard to win.