I wouldn't even know where to begin casting wise, but I'd be more interested in where the different songs and scenes would be set:
The "Prologue" could be all over the place (with the credits running over). "Beautiful Girls" would be on the stage of course (with a pan out from Roscoe at the end to reveal all the girls lined up). "Don't Look At Me" could be in the lobby (with Sally hiding behind columns to avoid Ben at first). "Waiting For The Girls Upstairs" would be backstage. The "Montage" would be on the stage again (along with "Who's That Woman." "The Road You Didn't Take" and "In Buddy's Eyes" would be in one of the boxes. I don't know where I'd set "I'm Still Here" or "Too Many Mornings" for that matter. I've always imagined "The Right Girl" on the roof, and "One More Kiss" somewhere way up high in the wings (though that's impractical since she's in a wheelchair most times, imagine panning up with that intro playing...). "Could I Leave You" would start somewhere and work its way back to the stage where the big confrontations would occur and the "Loveland" sequence would begin, lapsing to the alternate reality past. Then, the final scene would end with the four principals exiting the stage door as the sun is rising, and as they exit their ghosts appear still inside doing their final lines.
Of course the movie we all want will never be made, so it's nice to imagine how it would be. And we can imagine it with those incomparable original leads.
^My guess is that I'm Still Here would be set on stage and Too Many Mornings would be set in the dilapidated lobby when Sally and Ben think they're alone (sort of like the famous photograph of Gloria Swanson in the ruins of the old Roxy, which inspired FOLLIES).
Shirley Jones would be a great Heidi if she can still sing it! It would be great to see a star of classic movie musicals like Oklahoma and Carousel in a movie musical again.
"I saw Pavarotti play Rodolfo on stage and with his girth I thought he was about to eat the whole table at the Cafe Momus." - Dollypop
Now is it just me, or is it that Nicole Kidman is becoming like Carlotta, once a popular movie star who has turned into a joke? Which is probably why she could make a really good Carlotta if she can train her singing voice more and not have her sing I'm Still Here lower like her performance in NINE.
But movies aren't huge moneymakers anyway. No matter how much they "Meryl Streep" Into The Woods, it will never be a blockbuster. People who enjoy musicals and mothers with children will go to see it.
Looks like my prediction was way out in left field. I'll just skulk off to the sidelines.
If anyone ever tells you that you put too much Parmesan cheese on your pasta, stop talking to them. You don't need that kind of negativity in your life.