Hear me out.

I feel relic weapons and armor and Ultimate items should be treated like hairstyles and emotes. You would manage them through an "antiquarian". None of these items are functional once you have passed the patch in which they are acquired; and really they are more like unlocks given that they are ALWAYS class specific and cannot be stored like other items in general and often are more trophies then functional items.

So I simply suggest once you acquire one of these items they go into antiquities; option available when glamouring or displaying on Mannequins. This would also go a LONG way to preventing trophy ultimate displays from permanently eating up retainer slots and saving on the abnormal inventory management issue they introduce given that as it stands to possess all relic/ultimate weapons devours a large amount of glamour space and that will only increase as more classes are added.