The Great Divorce should be made into a movie.
It's been done as a one man show, but I don't know how successful it could be as a stage play. It would be o.k. in the first half - in Hell - but I don't see how anything but CGI could come close to Lewis's lyrical descriptions of Heaven.
The dialogue would be fine, though. Lewis had almost as good an ear as Kipling's for ordinary speech.