Multiple controllers/joysticks can be merged together into a single Controller instance. This would allow other joystick inputs to be handled as one.

This functionality could be extended to binds so each controller connected would have a different set of buttons, even if they are still identified as the same button: (e.g. J1-A would be the A button on gamepad 1).

I've decided to defer this for later as joysticks are a very niche part of the controller community and holding back 0.3 because of the major refactor needed for compound controllers to fit in.