When I was writing screenplays, I wrote romantic comedies. The first one was read by 17 agents and I had 7 offers of representation. One of the agents wanted to take my play and turn it dark because he knew Fox was looking for a vampire show and he was sure he could make mine work. I went with another agent because I couldn’t bear to darken the vision in my head. John Grisham’s NYC book agent, who subcontracted me out to Writers&Artists in Hollywood. 2 year contract but it didn’t sell and I always wondered if I should have let the other gentleman darken it.
I understand how hard it is keeping one’s Vision intact when dealing with the “Industry”. I am a Singer-Songwriter, and, while it is a delight to have someone else record my songs, I would hate to see them mauled beyond recognition.
But, when someone buys the license to record the song, or the rights to a book to make a movie, they can do whatever they want with it, unless contractually obligated not to change it.
“God Bless America” by Irving Berlin actually had such an ironclad agreement that the arrangement could not be tampered with. But that is very unusual!