he had a deadline yeah, but that doesn't mean he had to stick to the premise he had. Didn't Nick Meyer write a rough draft for TWOK in a short time?
Still, the "heart of darkness" story would have been better than what we got but that's not saying much.
Meyer wrote one of the drafts in a short time but I'm pretty sure he wasn't starting from scratch when he wrote it.
In order for Piller to start over he would have had to go back through the process of mollifying both Stewart and Spiner. When they had a release date before they had any idea of what the film was even going to be about, they were doomed to make a bad movie. In my opinion.