Rampage players can only attack other rampage players. Do this and remove all punishments and find another use for the prison system elsewhere.
This way, Nobody has a reason to complain. Because if they got killed then it's their own fault for entering rampage mode. Plus this wouldn't stop the Pk'ers from having their fun. They'd be able to pk freely without worry of in-game punishments.
It will still be open-world PK because you'd have to worry about the other rampage players, you would also have significantly more time to PK as well. Would anyone agree with this? If not then why so? If the devs are willing to adjust the game by "English voices" to the NA/EU release then why not switch this feature as well?
Or do you want the option/opportunity to attack and kill players in pve content/pve gear to remain? The prison system to reduce your PK and active game time to remain?
This is the worst idea that I have read in my life, you are not made to be a game designer for sure