> However, I think that they’re really worried about is that a person needs to design and implement that stuff… It throws a wet blanket on their insistence that this will replace entire people in entire workflows or even projects

You can have the AI design the custom harness in advance. It's not especially hard work! In fact, the AI could even come up with the workflow itself; it's a different and much simpler problem than trying to stick to it after-the-fact, with a filled-in context.