I just rewatched one of my favorite movies, Whiplash, a few days ago and couldn't help but think how well it could work on stage. I see it as a play, not a musical, and it could be a very faithful adaptation of the script. If you got an amazing Jazz band involved, and a very very talented drummer/actor to play Andrew it would be such a cool experience.
In terms of Fletcher I'd love to see Mandy Patinkin take the role. I think Steven Pasquale could be great too.