I think a better solution would be to put some kind of "hit counter" for the killshooter. Say, if X # of rounds hit a friendly, killshooter "activates" and blows up the offender. Otherwise, both planes are undamaged. This would prevent the problem of people flying in front of you to steal your kill and having YOU getting killshot!
Example:
green1 following red1 , distance is d400.
Green2 barges in to steal the kill, flies in front of green1 and starts shooting at red1.
Green1 was firing MG's when green2 dived in and hit green2. The game counts how many bullets hit green2. Count is below the X #, no killshooter happens.
Later on green2 is a bigger jerk and thinks its funny to shoot his own side, he fires a good burst at a friendly, count is above X #, he gets killshot.
It would also be very usefull if friendly collisions were ENABLED above 800ft. Below 800ft they'd have to be disabled to accomodate people landing and taxiing or large groups taking off together, but above 800 , they would collide.
This would also prevent the "fly through friendly plane" to steal the kill AND killshoot the guy he's stealing the kill from.