Wait what happened to the last thread like this?
I am thinking that what you will be able to use as gear for vanity, will be restricted to whatever your class/job can use as stated by the gear itself. You wont see Gladiators and Marauders wearing robes because they can't wear them, same thing with DoM and actual armor. Makes sense to me and still leaves a wide variety of vanity gear as well as options.
I do hope they include weapons in the vanity slot. Otherwise I'll never have a reason to use the LR:FFXIII gear, ever, once I level all my classes beyond a certain point.