Not to sound confrontational but pray tell what new moves and abilities would you have added that would enhance gameplay and also not obfusticate the already balanced, free flowing abilities present in the game
The way I see it there's no way to add new abilities without a) doing that old video game trope of convieniently forgetting all your moves and having to relearn them, i.e., redoing everything you just did in Origins, or b) introduce new mechanics in the form of gimmicks, which in this games case came in the form of Murfy, the chicken levels and the Wizard glove shooting power up.
I'm not saying it isn't possible to add new moves to the repetoire, just that Rayman's movepool for Legends (and Origins) seems completely adequate for all situations the game can present you with, adding more would be gimmicky in itself.