Considering glamour is really just replacing a gear's look for another's, why can't we just "register" the gear into a menu and be done with it?

As in, you get piece X. Piece X is now registered in that menu as you having worn it before. You then spend glam prisms to change your appearance from that menu.

Hell, it'd be lenient on the code and inventory anyway, since you turn glamour into a checklist no different than the Triple Triad cards menu.

I mean, sure, it'd make re-running older dungeons moot, but when you can get virtually the same dungeon pieces through crafting, it already dilutes the purpose of running it. Sure, stuff like the Skalla gear and the new version you can craft aren't the same; they dye differently. But that alone already means some people aren't running Skalla for the model itself. Plus, with a glamour dresser, you only need to run the dungeon to an extent until you get the drop. After that you're putting it in the dresser and call it a night. It's literally the same thing.

Re-running it implies that you either lost the item\threw it away or you're into stats for some reason. And afaik that hasn't gone away, even with the glam dresser.

"Oh it's because of lore" -> That's moving the goalpost. So much of this game has been changed to fit player demand anyway, lore be damned. And lore can always be retconned anyway. Is this Final Fantasy or Final My Immersion?