You have some assumptions here

> first step should always be to run an AI against them

What if they write an agent which takes the feedback and resolves them with a new commit. Which again didn't do anything other than offloading more to humans who are reviewing.

> each dev should come up with their own prompt for AI PR review and they can switch off who reviews it each time, until there are no problems remaining.

This assumes AI reviews are correct most of the time, if so, why do we need even humans. Why not have repository level code reviewer which is run immediately after code has been created?

regardless of where you move it, there is still a bottleneck: humans.

If you don't remove them, you will just pass the ball between agents and at the end of the day human still needs to review it.