This sounds good in theory, but in practice, a person capable of doing a good job at this role would also be a good developer whose impact would be greater if they were churning out code. This is a combination of a lead engineer and SDET.

In reality, this ends up being the job given to the weakest person on the team to keep them occupied. And it gives the rest of the team a mechanism to get away with shoddy work and not face repercussions.

Maybe I'm just jaded, but I think this approach would have horrible results.

AI code review tools are already good. That makes for a good first pass. On my team, fixing Code Rabbit's issues, or having a good reason not to is always step 1 to a PR. It catches a lot of really subtle bugs.