The correct way to make a vanity system is to have a second gear window where anything you put in the window overlaps the display of the actual gear window. This would include the same restrictions on gear such as job classes, gender, and amount of slots needed (odin's armor for example)

The biggest draw back for the way they did it, is many classes share gear. My paladin and my warrior both use allagan boots and thus need to look the same because I can't have my allagan boots look like 2 different things. The way it should have been done is the same way they did gear sets, just with vanity sets equipping a different job would swap the set and you could have different costumes.

I'm not surprised they messed it up, ever since they announced we'd need a crafter for the system I knew they were doing it wrong.