I'm one of the guys who flys Warbirds who'd prefer never to see killshooter turned on, and it also might interest you guys to know that we've had killshooter off for about a year or so in the WWII Arena, and there have been few incidents that warrent notice.
Of course there will always be the occasional love muffin that will deliberately kill a friendly, but I quite prefer not needing to be controlled any more than necessary. It also adds a bit of immersion by allowing friendly fire accidents, and doesn't reward the other love muffines who like to jump down in front of someone who's saddled up on a bandit and about to fire, or punish the guy who was saddled up. All in all, most of us prefer it to killshooter on. There is a small, very vocal minority who'd like to see it turned back on, but I suspect some of these may belong to the latter of the two types of love muffines described above. There's no evidence that turning it on is at all needed, and I can think of, at most, 3 to 4 incidents in the last year that would even make one consider it. For the most part (probably 99% of the time), when someone dies to friendly fire it's due to the fog or war, or purely accidental. Not bad for an online game. Of course I don't feel AH would be able to turn it off. Too many players to police themselves as Warbirds has been able to.
By the way, when AH gets the new WWII arena open, where there's a strat layer in place and more of a point to Aces High, I'm going to give it another whirl.
[edit]
Just wanted to add....what's the point of killshooter? If you don't want friendlies to be able to shoot friendlies down, just turn off friendly damage, rather than have it "bounce" back into the person who pulled the trigger. Seems more like a sick joke than anything else.