Princess Lily in the movie "Legend" was originally supposed to be transformed into a demonic werecat:
https://www.figmentfly.com/legend/script3a.html . Much as I liked Lily's Darkness dress transformation, an eventual full demon transformation would have been nice.
Speaking of 80's glam-fantasy movies, in "Labyrinth" it was a bit disappointing that the Goblin King didn't turn Sarah into a goblin princess during the masquerade ball scene.
Kind of a weird one but, I thought they were going to turn the heroine into a silly sexy tomato minion in "The Adventures of Rocky and Bullwinkle"
https://www.youtube.com/watch?v=fC8SCqV_v_Y but nope.