Something that could work is AW's old 'persona non grata' system with some addons.
The way that worked, if you shot down two or three friendlies, you got no ammo or ord for a few hours.
Add to that, for AH2, if you damage a friendly you take the same hit to perks as if you had crashed/bailed/ditched.
Shoot a friendly down, and you get no perks that sortie, no score, and your name does not show up in lights.
Figure that might be enough of a deterant for the score-mongers and dweebs alike.
Now, KS as is works pretty good. I'm just tossing in an idea.