I'm not suggesting using AI generated code as a proposed design.

I would try and get an understanding of design space by giving a good agent a high level goal and seeing what it does, then getting a summary of the approach.

When you do this several times, especially if you give it a steer on some non-functional requirement, you can compare and contrast different approaches.

The idea isn't to prototype so much as to gather information by doing. Prototype, to my mind, suggests other things; shortcuts, stubs, incompleteness. I would actually ask agents to do the whole thing, and find out the full scope. It can be particularly useful revealing side effects.

Pair it with code auditors wearing different hats, of course.