I would ask for a 'faith' system where behaving according to the ways of the main worshipped god, e. g. for beast-people behaving peacefully, greeting other and not attacking anyone and anything in sight unprovoked is rewarded by this god, so that the character is protected by his god in his home realm, when instead of fighting he turns to praying to his deity. If he has proven his faith before, then he is protected, if he tried to pk himself, a peaceful god would not protect him. If one wishes to join in the fight, praying later should not be an option anymore to escape from a fight. In that way you can add a role-playing component, where choices matter and add a protection for players who wish to avoid pvp at all cost, but have to behave more in consent with their protective deity. Respectively, in the demon world deities or archdemons of chaos and destruction would support their aggressive, backstabbing followers with buffs for fighting, as this is their realm and the other gods have no saying there.
This would help with the PK debate as well as adding some roleplaying flair.