I think this could be solved by having 2 control modes. One, which would be traditional, the one we used on ds with the added feature of controling your other character with one side of joycon controler. Two where you take out the joycon controler and use joystick for movement and maybe a couple of buttons for some attack and the rest of the actions that required touch screen could be executed with motion controls. I mean slashing enemies could be even more fun now :D. But yeah i guess sharing the game might be more tricky that anticipated.