I like the on safe zones, maybe with like a green circle outlining the border, but make it so that you can't just jump back in.
Or have PvP as a status effect (think OW-slime type thing) where once you step in it you've got it for like 30 seconds and don't lose the effect while in combat stance (like if they follow you in you won't lose the ability to fight mid-battle). Don't know a fair way to prevent people from ley-ing out though lol.
^^this is good idea.Issues would arise with conflicting names -- could be addressed by prefixing "(SERVER) "!
(:D thinking of people that have toons on different servers with the same name that could fight themselves lol)