Actually, Kristen Bell would be more suited to play Elphaba. Her claim to fame in VERONICA MARS was based on the idea that she was the outcast, the anti-popular girl. She played the bubbly type very well in REEFER MADNESS but that was always with a wink to the audience. Her belt is probably not strong enough to sing the score as written, but if they lowered the keys and adjusted the score for her voice, she would act the hell out of the part.
On the other hand, Hathaway's soprano could make her a candidate for Glinda.
"Some people can thrive and bloom living life in a living room, that's perfect for some people of one hundred and five. But I at least gotta try, when I think of all the sights that I gotta see, all the places I gotta play, all the things that I gotta be at"