I know there is another killshooter thread going, but I would rather have my own thread about my idea.
Why not keep the killshooter system just the same but instead of chipping away at yourself by shooting a friendly, you simply die once a fatal amount of damage has been done. This would prevent damage from the unintentional friendly fire, especially when somebody dives right in front of you just as you fire. And when you die, you get a little message saying it was a killshooter so your aren't left wondering why you suddenly died.