I've noticed that most of the time no one even responds to "friendly" anymore, because there's no drawback to killing and taking someones stuff. So here's my suggestion: A harsher consequence for those who kill a lot. One example might be zed encounters. The higher the kill count of the bandit, the more likely zeds are able to spot you even in crouched mode. Something to do with them smelling blood on you. Or zeds going after a bandit with a high kill count rather than going after someone who has lower or none.