Hi Andy, Seriousness is not a prerequisite for posting on this thread. Let your imagination run wild. Johnny Depp is an intriguing and thought-provoking choice for Rhett Butler. I'm trying to get a mental picture--it's happening.
Yes, Streep is too old to play Scarlett, and Teri Garr is too old to play Melanie. Cate Blanchett is a good actress, but I can't picture her in the part of Scarlett. Deb mentioned her for Melanie. I think that's a better fit. As for Prissy, I think a good actress could make the part her own. But some are harder to picture than others.
What about Jude Law as Ashley?
So far, we've got some rather "interesting" suggestions for Mammy--Bette Midler, Barbra Streisand, and Marlon Brando.