Switch the controllers inputs for single-player games like with Retroarch
I was looking for a tool to do what you propose, so it's only natural that I'm upvote the subject.
This is exactly what I want from this program. First of all I think it would be great to have an easy way to "hand off" the controller to a friend like you would in real-life or on PS4 SharePlay. But it would also help because I recently ran into a glitch where a virtual Xbox controller was still connected as Player 1 after I ended a Parsec session, so I couldn't use my real gamepad for anything until I reset my computer.
also it would be useful to share a controller too
Essentially setting which player belongs to which controller.