Hmm, interesting idea, to ask the user to provide the overall intent by making them edit/write the plan, since the LLM can't do intent.
But man, we've recently had a number of programming beginners join us in our relatively large codebase, and I've basically had to write such a plan, i.e. step-by-step instructions, for them many times.
It just means that I go through the whole codebase and have to think everything through, without doing it myself.
It often took similarly long do that, and formulate instructions, as it would have taken me to write the code myself. Because obviously we're using a high-level programming language, so there's not many detail problems which are easier to describe in a natural language.
It's also incredibly difficult to provide correct instructions that way, since I don't get to read the existing code while I write the code.
And reviewing their code to figure out what came from it, that binds even more time.
So, yeah, it really doesn't sound like this LLM thing would save me time either...