Suggestion: De-glamour Plate

[Niwashi]

It overwrites the current glamour with the plate glamour

Sometimes. It depends on whether the gear itself can accept the glamour.

For instance, if you're currently on BRD and wearing gear that's wearable by both bards and machinists, a glamour plate with Machinist specific AF gear would work like you described, because MCH AF *is* compatible with the gear you're wearing, even though it's not compatible with your current job. So the glamour would be applied to the gear, but wouldn't display.

If, on the other hand, you tried applying a glamour plate with Paladin AF to gear only wearable by Bards and Machinists, it would have no effect, because the gear won't accept the glamour if there's no overlap between who can wear both. (I've made use of this by using one of my crafter gear glamour plates with a combat job when all I wanted glamoured was the earrings, which happened to be the only "All Classes" gear on that plate. It glamoured them while leaving the rest of my glamour alone.)