Is there any way to make the controller the player 2 while the player 1 uses the keyboard?
It’s not possible. The engine doesn’t doesn’t allow port remapping, so there’d need to be a second controller connected to allow P2 to use a gamepad.
Shame, at least I managed to connect Joycons to my PC. Also, if I may suggest, can you add the cart mechinic from MP 9 and 10 and the card mechanic from Sonic Shuffle? I think it would be pretty cool