As a general idea I like it but NPC's should be a bit deeper and not just take revenge on everyone on the basis who killed who. They should also see justifications for otherwise reprehensible deeds like killing one's entire groups and just saying that it was self defence it's ok. We can't expect everyone to be like that, some people only see family and gang ties, but some people might feel bad about what they were doing. Maybe when that ghost of your past captures you he comes up to you and says "Yo, remember me?". Then you have a dramatic silent moment and in a moment the other guy just says "Aaaah, gotcha man! You should have seen your face!" and he tries to be friends with you which might be genuine or he might be trying swim up you sleeve. (Do you say that in English? Basically I'm trying to say he's an ass licker.)