Okay This has been in my head for some time and so I've decided to share it with you all. I have an idea of how the story of Swan Lake would work for a Disney version.
Odette who is a young princess runs away from home to escape pre-arranged marriage and ends up captured by a young powerful and yet spoiled sorcerer named Von Rothbart who enjoys cursing people.
He puts Odette under a spell that keeps her a prisoner at swan lake, by night she is a princess and by day she is a swan. She is still able to rome free but unless she is around the lake before sundown the curse will suck the life out of her.
Moving to a couple of years later introduces a travelling sorcerer and his young apprentice who seems unsuccessful at casting magic. One night the young apprentice ventures off where finds Odette. He promises to help her break the spell and rejoin with her family. At the same time the young apprentice falls in love with her.
This is just a rough idea but the rest is much more bigger and better in my head.