There is no PM. There is no reason the combined talents that exist can’t do everything a PM is required to do.

Or, he levitates above this mythological scenario and flies to Olympus.

I read some of the other responses and I really don’t see their need in this fantasy you’ve concocted.

Good design sets vision. Vision easily converts to a roadmap. Data determines tactics.

If you need a liaison to the business this could be the service designer pretty easily.

The issue though is that this is fantasy and a good PM doesn’t liaise w the business. They ARE The business. They also are best at driving a backlog owning decision making and prioritization. A good PM is the PO and the agile coach. They run the business of the product.