Would it be hard to implement a feature where if someone wants to hostile you, you get prompted to accept or decline? And be able to De-Hostile anyone if you accepted by accident. As well as OP said, make it so passively players take reduced damage from players.
Personally I don't care if pvp is balanced or not, as OP said, I just want to be able to duel my friends and make some different pvp builds. I may be apart of the minority that wants pvp, but it really doesn't seem like a major issue to bring it back, maybe i'm wrong. I know it gives another option for end game, I personally don't care to do all the end game pve content, I just wanna pvp like in the old D2 days