GPT would be a lot more useful if it were able to mark sections where it "isn't confident that it can do well". Another thing would be an iterative approach that includes compiling and testing the code.

Essentially, you want to build an artificial programmer ("junior dev") who can work with a better developer/manager. That seems to be the way in the short-term. Doing this by just single-shot text transformation is a lot harder. Humans can't really do that neither.