I'm working on a mission that sounds pretty much like what you want. In real life, most units (with the exception of special forces) don't really have individual radios for each member. In my mission, you can communicate via either hand signals or via shouting. Shouting will alert any enemies around you as to your presence, but hand signals have more limited range.
I work it like this: I (the player/leader) am the only one in my group. There are three groups of four men (fireteams) that follow me, and another group of one man who is my radio operator. Each group is in a custom formation, and the three groups follow me in a custom formation (either a column or a line). I can command the groups to spread out, or bring it back in.
I tried using the knowsabout command for the hand signals, but it isn't working out as I wanted. For one, you can't get the units to look around as they move, so if they are moving in formation, they can't see your hand signals unless they are right behind you. Also, bushes and trees have no effect on visibility, so if you are in the middle of a forest, and can't see your squad, they could still see you. Basically, I've given up on the idea of using knowsabout, and instead have just used a simple "is he 25 meters or less away" method.
I've only really begun to work on this, so I don't have very much to show for it yet. But what I have is very promising!