Recently I've been spending hours reliving my youth playing snes roms on SNES 9X. In fact I liked the 'app' so much I went and brought a second hand wii classic controller. This made me wonder whether there is a tweak to be able to use BT Stack and the wii controller with standard iPad games which use the onscreen joystick type controllers. Does anyone know whether there is a tweak avaiable?
Nope, nothing like this which I am aware of. The only support I've come across are in a few of the emulators like you have discovered for SNES 9x.