Runescape is one of the longest standing MMO’s with an active player base. One thing they do is have a part of their world dedicated to PVP called the wilderness. In the wilderness players can fight each other and loot others gear that they find after a player has died. I think something similar could be implemented in the server.
There are plenty of spots on the map where players rarely go to and would be great zones to be considered PVP active zones. Players should always be aware that these zones are pvp areas. If a player wastes another player then they should be able to loot the weapons and any illegal item that the downed player was using.