On Pokédex lore, if that's anything to go by, Banette is a child's neglected doll that has been possessed. Even possessed items by poltergeists don't suddenly become transparent. I see where you're coming from, but Banette is more of a physical thing rather than an ethereal ghost type, such as Gengar.
guuhh O_O I still love this even though it will probably give me nightmares its fantastic! The detail is phenomenal, the button eyes are genius! The whole look gives me a Scarecrow-batman-villain vibe, with the stitching and that look like that pin is destined for my soul O_O