I think Jennifer Laura Thompson is a great choice. She can be serious and eccentric all in the same sentence.
And she's beautiful and she can sing.
As far as any major star casting, or stunt casting... I wouldn't look for that. This is Disney, remember. If someone such as Kate Winslet played the part, you'd have a stampede at the box office, and they would be hard pressed to replace her with anyone that isn't a "let down."
Disney doesn't "star cast" anymore. They want their brand name and the show itself to be the star. Then, replacements aren't that big of a deal... it's a franchise show and can run forever.
"Jaws is the Citizen Kane of movies."
blocked: logan2, Diamonds3, Hamilton22