My one concern for that which would be comparative to open pvp against the npcs is that too often I click on them intending to talk to them and get the "so and so is invulnerable to attack".
This is part of the whole issue I have of allowing players to attack each other, but having guards protect them. The bounty hunter, guard, jail system is a popular topic of discusion, but few take in consideration the potential for mis-clicks and bugs. If you have a "safe zone" in the game, just make is so it is impossible to attack. This is the most fool proof way. I personally have been killed by trainers and guards in other games many times from mis-clicks, usually from questing, and have always whished at least my trainer would just stun me or something instead of the insta-kill. Thankfully, PS does not have such a thing. Implementing any kind of guard protection would probably change that.
It is realatively easy to have a safe zone and a rpk zone, anything inbetween is much more complecated to do, and typically introduces more bugs, exploits than it fixes.
