Basically the rule for whether you can apply glamour plates or not is, are you on a map that has any enemies in it? That's why capital cities and the Gold Saucer are fine, but but Revenant's Toll isn't because it's part of the Mor Dhona map. If the Bronze Lake changerooms took you to a separate instanced room like an inn, you'd probably be able to use them, but you're still in Upper La Noscea so you can't.