Personally, I think that to have True Faith it would have to be something that the Universe responded to. Especially the True Faith powers that already exist. Guide My Hand, Bless This House, etc, seem like things that would need power to give the practitioner. The Faerie Courts could probably do it, as could Magic, religions, certain other philosophies and Beliefs, but I would be afraid of opening it to wide, because of things like "salad dressing." Because there is no way that believing in a type of salad dressing would lead you where you need to be to fight.