I'll need to noodle around on it before posting a true response -- but for now all I have is that these observations are spot-on.
And I do know of one playwright who walked away from a commissioned thing-a-ma-doo before prodution -- and that was Suzanne Lori Parks -- although I don't recall the details or the play -- it was earlier in her career -- and people thought she was making a big mistake because it was going to put her on the map. She wanted to keep her play her way. So she walked. And kept her voice intact. Her career has worked out okay anyway... so you don't always have to roll over.