I agree that Love and Mercy is a terrific film, and I could not imagine Brian Wilson's story being told any better than it was in that film. However, there is no end to the number of compelling stories that could come out of that era of music. There is a short documentary on YouTube about Steve Goodman (composer of City of New Orleans), and much of it is devoted to accounts by Kris Kristofferson and John Prine of this magic night that catapulted the careers of both Goodman and Prine. I've watched that documentary a number of times, and every time I see it, I think of how great it would be if the right people could adapt the story of that one night to the stage. The idea of combining the story of the unique brotherhood between Goodman and and Prine with their brilliant music, as they navigate the Chicago music scene at time, with a backdrop of familiar names like Kris Kristofferson, Johnny Cash, Arlo Guthrie and even Paul Anka.....well, it just seems like a story that needs to be told on stage.
My point is that the great stage adaptations are not likely to be found in stories about people whose stories have been told many times before. There are some really great opportunities for storytelling lurking just beneath the surface of the music legends. People who are the legends we didn't know about.
I'll just maintain a sliver of hope that it will happen one day, hopefully while Alex Brightman is still young enough to play Steve Goodman.