Actually, a lot of the people who are hating on Nelly do not realize that vocal range that she posesses. Honestly, she actually sounds like Idina, and (being that I have seen her in concert - twice) has an AMAZING belt. She does have the voice AND potential to play Elphaba.
The reason why she will not play Elphaba: Nelly is all about originality. She is a gifted song writer who takes pleasure in writing her own stuff. I think it is too early in career for her to want to do "other" people's work, including covers, and Broadway shows.
"Do you know what pledge time is, Andrew"? said the PBS Executive.
"Yes", Lloyd Webber replied. "My 50th birthday special must be one program that gets done a lot."
"No", mused the man from PBS heedlessy. "Not so much. Our Stephen Sondheim Carnegie Hall concert. That's a big one."
Spoons, forks and knives seemed suddenly to suspend their motion in horror, all around the table.