mikejmoffitt wrote:
But there are ample NES controllers
Not ample forever, and third party controllers such as Retrobit lack a certain feel. Relying on anything that wears out mechanically and cannot be replaced, such as the dwindling supply of NES controllers, is a bad idea long-term.
In any case, there's probably a way to do this without destroying a working Game Boy, and it involves making a Game Link to controller cable and a program to emulate a controller. As I understand it, both the NES controller protocol and the Game Link protocol are just SPI (clocked serial).