History Fashion Belle - Rococo

I got to thinking, Why do all Disney princesses have such odd outfits? why don't they match what I know of fashion's history?
So i'm making it a project to make them what they should have been in the movies, taking away all the fads of the century the movie was made and replacing it with the fads that suit the origins of the costumes I can best alter them. Lots of researching.

Here's Belle from Beauty and the Beast in 18th century Rococo fashion.