I seriously wish they'd have cast Liam Neeson as Anakin. Retaining the look of Qui Gon, Neeson definitely had the build/size of Vader and three films with adventures of a more mature Skywalker who would have been difficult to train would've been great.

The one thing I really hoped for in the prequels, which we didn't get, was a great double-act relationship between Anakin and Obi-Wan. Two older actors could've given us that. Something along the lines of Harrison Ford and Sean Connery in Last Crusade.

Obi- Wan could've been the same age - after all they were more friends then anything.

Neeson's age would've tied in to Sebastian Shaw's in ROTJ as well.