problem is, there is more or less no way to "deal" with pk's/gankers in game which doesnt have permadeath (or at least jail where you can throw captured pk for extensive period of time when he/she wouldnt be able to do anything at all)
i would deal with it this way:
there would be 3 types of players:
1. "white" - nonpvper
2. "blue" - pvper (switched on pvp flag, cd to turn it off would be 1hr)
3. "red" - pk (red flag would go off after 24 hr since last PK kill)
killing red player would be ok and anyone could do it (only if it would do white player, it would turn on his pvp flag)
killing blue player would be also ok, but if a white player would attack blue player, it would turn on pvp flag with 2hrs cd
killing white player would give you a red PK flag.
what is the catch? if you die as a red flagged PK, there would be 1% chance of permadeath