The Armoire Update

[Canadane]

I wish they'd also let us store the relic weapons/gear in the armoire

The items stored aren't the "same" item in the sense that when you give an item to a retainer and take it back it's the same one.
The Armoire is just a big checklist of "did you have this item? Y/N"
Meaning things with customizable stats are unlikely to be given way to armoire storage, as much as I'd like them to be too.