Darkness of "Little Mermaid"

Disney's "Little Mermaid" DVD has a great extra, a pencil test of the scene where Ariel makes the deal with Ursula (this youtube link is for the scene full color, still pretty good). Dark stuff. It's an evil scene, the climax of which is downright violent(when she gets her legs). This is what animation is capable of portraying, emotion on the level of any live action movie, perhaps beyond. This may be the greatest Disney Villain scene of all time. The problem is that nobody ever explores that dark place, build characters around it and tell a story from there. Why did they have to make the color and lighting all bright and fuzzy? (thats why it's better to watch the pencil test version). Imagine if Disney didn't have the whole kid thing attached with it. I wish Scorsese directed that film.(btw supervising animator for Ursula was Ruben Aquino)