It would be great if someone with the proper knowledge would modify the Sega Mega Drive gamepad (the only one that really works as a gamepad should work) so that at least 2 buttons are working as fire 1 and fire 2 - the same way as C64 GS, not being harmful to C64 in any way. I guess it is only a matter of what to (dis)connect where + perhaps some slight modification in some components in the gamepad...

But are there any games that use second fire/action button?
Better just disable that second button or do auto fire like I did.
_________________

Yes, of course. The games released for C-64 GS console have second fire button support for that Cheetah joystick.