In my opinion they need to do what FFXIV does, they have weapons from dungeons/raids..etc like normal BUT they add a "relic" weapon with a long quest/story that is slightly less powerful than raid weapons BUT you can always upgrade it after each patch keeping it close to the best in the game.
This allows people to ever farm weapons from dungeons, raids or just do their relic (in this case artifact). They don't even need to have unique skins just a weapon you upgrade ilvl ever patch.