I like the thought of not knowing the adversary, it might add some new to the game. Personally i would prefer no communication or cooperation allowed at all.
However in the end it should be known who played which position, including dropouts! I like to know who the backstabbers are.
I played other war games than vga with such a set up before, and sadly the cheating was rather obviously. Outside friends where cooperating faster than in game messages would even allow them and before they meet each other.