The other options would be insanely gamey. No damage to either, or say 3 friendly kills per day would just be BS. In RL pilots did not shoot over their buddies shoulder trying to steal their kill, and it happens way too much in the MA even with KS.
I think I have kill-shootered myself about 3 times in, what, 8 years? If you have problems with kill-shooter, frankly, 99% of the time it was you own fault, plain and simple. I think anyone foolish enough to shoot a friendly deserves what they get.
Seriously, if this was ever changed the wailing and gnashing of teeth of those shot down byt their own team would be deafening.