[EricH]

That's kind of an interesting idea. If I was to make a suggestion...

Have it coaches-only, at least at first--the 3 coaches on the alliance all get a headset and talk to each other, with the option of keeping drivers' instruction "off-mike". But also give the refs (head ref or appropriate substitute) a mike-only interface, so that they can call a foul in straight to the coaches as the foul is dished out. Something like "Hey, Red, back off or get a pinning foul in 3... 2... 1... Tech foul!"