I think this simple flagging system would make everyone happy. PKers can flag in a city where they become gray/red or whatever. Blue players who don't flag can see who is a killer. And two players who are both flagged for PvP can kill each other without consequence. Flagged players also get less penalty for killing blues. But if you don't flag and you kill someone you get a much harsher punishment. This way it encourages pkers to be able to fight each other and also makes it easier for anti-rpkers to kill rpkers by graying up too. And it makes it so blue players can more easily identify killers. I think it would be a win-win for everyone