I've found the general consensus in AH is that cheating does not really occur as much as one might think (regarding ratting missions). When large dar bar appears a couple of bases back, any alert player on the opposing team will see it and deduct a mission is IB. NOE missions are a different story, but bases start flashing when you get close, and again the alert player can point it out.
As far as preventing people from PMing or speaking on radio 200 while in mission, I doubt that would really work. If a guy wanted to, he could up with the mission, then bail, then send the PM or talk on 200. Or for that matter, just see what base the mission is leaving from w/o even joining.
Even if you implemented the changes you are talking about, what is to stop someone from using a cell phone to call their friend or whatnot.
Anyway, for every measure, it seems those dedicated to spying can find some countermeasure, so the problem is insurmountable IMO.
I think the most effective deterent for this sort of behaviour is it doesn't seem all that entertaining to me, just sitting around in one country, just to warn your friends in the other country of a mission...not even getting to fight off the mission...(yawn)
Also, it is hard enough to get folks to join the mission to begin with, most folks just want to get up and furball or do their own thing. Based on that I just don't see the dedication to try and counteract the mission..if that make any sense.
Anyway, just my 0.02