Hello. I know it's not an unique idea and it has been written, but i want to suggest it in other way.
I suggest you to create a duel mode function for players to use. Similar to arena, but no arena points, no items to buy and etc. It could be like this: you challenge opposite side player or your side player, both of fighters can attack just the player they challenge, and other players can't attack and disturb fighters. They can choose to fight for gold or for free. Fighting place could be anywhere, or in places like PvP caves.
Player that die in duel mode can respawn in the place he dies, if he don't cancels the duel mode, so he can fight again without going long way back, like most of people does. No potions could be used in this mode, no scrolls and other things who can be easier way to win. I can explain my idea more, but i think you got this. I think this is worth to think, and i am not alone who want this function.
Your friend, Zaibax