As for me PK and PvP should work like this:
If someone kills another player without his permission
he becomes a criminal and would be chaced by guards in any city for some time (maybe 3h and maybe in some places outside the city too).
After PK, victim dies in a normal way and loses equipment and stats (PK can steal all of his victims stuff).
But after doing it, PK will be forced to live outside the city for about those 3h.
if he commits another PK in that time he becomes a murderer ----> UO.
Murderer should last for about 9h, then he becomes a criminal and after next 3h he returns to law abiding character...
As for PvP, if both side would agree to fight, winner should get little expirience for his fight and loser shouldn\'t lose anything.
As for guild wars, itr should work as PK but winners shouldn\'t be chaced by guards (but they can steal the stuff).
Maybe it should change if for example: chaos guild attacks guards or something.
Then chaos should be chaced by guards for every kill.
Sorry for my english.