I'd love to see Toni Collette play the role on stage, it'll never happen just practically speaking (there won't be a revival any time soon obviously), but while I think she'd be fantastic she has already played something along those similar lines in US OF TARA. Diana is not the same character, but some of the issues explored in NEXT TO NORMAL were explored in that show, I'd love for someone who hasn't "gone there" yet to get a crack at it to come up with something completely unexpected, Winslet and Watts would be perfection. I know Naomi Watts often talks about how she gravitates towards really intense roles, she'd match Ripley in terms of emotional complexity, but I can't imagine her having an interesting, let alone powerful, singing voice. That'd be a huge problem casting the film for me, I know Ripley got a lot of backlash for her singing but I was thrilled with the raw vocal performance she gave the night I saw the show. Not sure what Hollywood actress could match that in a movie musical.
"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"