Keke Palmer and Dove Cameron are my Elphie/Glinda pairing. I don't know if she has the full top belt, but Keke has a great voice and I think would be a fresh, comedic Elphaba with the right amount of joy and gravitas. I think Jessie Buckley would be pretty inspired casting, and I wouldn't be shocked if Zendaya was mentioned. Let Ariana play Nessa, with Christine Baranski or Jenifer Lewis as Morrible.
"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