FWIW, you can put an item in the glamour dresser, set up a glamour plate, then remove the item from the dresser. The glamour plate will still remain. I've done this to use a piece of current gear in a glamour; my alt is wearing the Exarchic fending set, and though I have changed the glamour on the boots and gloves, the coat and pants are using their own appearance. But I didn't want to look to break when replacing things, so the coat and pants were thrown into the dresser, used to make the plate, then taken out and equipped again.
The one downside is that you have this weird situation where the item shows as glamoured into itself, but that's fairly minor.
