Some time ago I saw a post suggesting a change in the duel arena to make it by teams. Well, what I'm suggesting is to keep the da the way it's now (1 vs 1) and to add a Counter Strike zone, in which the action would be based on two teams and there would be walls, containers and other objects to take cover, no vehicles and the players would be given some weapons like AK47/M4 and more ammo to their sawns and uzis, but when you exited the CS zone you would have your previous weapons again (like in rampages).
Besides, this suggestion fits perfectly with the DM idea of the server.