What if relic weapon was created and upgraded like ARR/HW but could be augmented to give bonus stats to specific content e.g.

Make a weapon have basic stats primary/secondary
If you do PotD/HoH like content you can augment the weapon to have bonus + 200 main stat while doing that content
If you did Eureka like content you can augment to give it Eureka like buffs and only activates for that content
Could do same thing with Fate system, Leves small secluded stuff essentially

Now you would need to put an extra reward in to incentivise players to do everything with the weapon like a title/mount

EDIT: basically a weapon that could through effort be the best weapon for everything within an expansion