Bruh I literally could do it with a single command block. It's not that hard you just apply a single NBT tag to every weapon. (Even the plugin OldPVP does it) Either way bringing back the correct pvp doesn't fix the fact that they're pvping for no reason. What do they spend their money that they earn on? Why bother getting god when the market for it is already dead. The server has no outlets to buy into, and so a pvp economy cannot exist anymore, regardless of the version it's on. Fix the server then fix the pvp, perhaps that might bring back pvpers xd
~ @legendcaleb
Sorry to break it to you, but you simply can't apply an NBT tag to "every item" without scanning the entire would for items (which would take ages) and modifying them all. You might be referring to items in loaded chunks or in player inventories, which is a different case.