First off I have seen the idea gm intervention work well, in the first semi massive player game I ever played, a mud called Legends of Terris. The GM's were gods, they enforced the rules that were not possible to hard wire into the game, added alot to roleplay, and and some of the plots going on in the game. They also mediated disputes that got out of hand. While that mud was not pvp, it however had alot of nasty things you could do to people. The "gods" were in general a positive influence, though at times biased force in the game. They allowed for the rules to be loose and yet could step in if things got to out of hand. I would love to see PF online try something along those lines. Their will always be ways to bend/break the rules intent while still keeping with in the letter of them. From reading the boards their seems to be groups of people intent on doing just that, and consider it just part of the game. While with in limits that is fine, when it gets out of hand I think there should be someone to step in. Trying to make rules that have no exploits is not possible and will just end up making the game to restricting while not actually succeeding at their intent. Anyway it likely not a workable idea but one can hope.
PS I was one of the people who used exploits, nasty tactics, ect, and was call before the gods various times, 95% of the time it was justified, I had various in game punishments, and only once was banded for a short while. So it not like i do not understand people wishing to find ways to work around the system intent, it just if it goes to far it make the game no fun for anyone.