What about a stage adaptation?
With the mania for all things mid-century these days, I was thinking that this would actually be a film that might adapt well to the musical stage. You'd have to punch up the triangle between Brad, Johnathan and Jan a little more to give the plot more heft, but otherwise I think it would work great. You could even interpolate a couple of Day standards into an otherwise original score. And imagine what a set designer could do with the film's finale in Brad's apartment!
Castingwise, I'm thinking Hugh Jackman would be great in the Rock Hudson role. (He does Broadway between film commitments, so it's not out of the question and it guarantees box office.) Extraordinary stage talent Kelli O'Hara would be wonderful in the Doris role. Andrew Rannells of "Book of Mormon" fame would be ideal in the Randall role and I was thinking Linda Lavin in the Thelma Ritter role.