Huh, well, I never had anything Sega related so that explains that.
I'm not really looking for "button 9", I'm looking for a constant set by the engine I'm using. (which might be button 9 I have no idea)
And regarding backspace not clearing the controller keybind, I've now tested it and it actually does as long as you're in controller mode when pressing backspace, if you press a keyboard button other than backspace before pressing backspace, then it will clear the keyboard key instead.
So you have to press a controller button to enter controller mode and then press only backspace to clear a controller binding.
There is however some issue where "select" is not working as intended, it just gets detected as a menu button press instead of clearing a binding.
But both of these problems will be largely irrelevant after my intended fix listed below.
As for using another button to clear bindings, I'm just going to have backspace clear both the keyboard and the controller binding, that should solve the problem.
I'll be looking into changing how keybind conflicts work, it's probably either going to be the way you described or the way I mentioned in my previous comment.
Yeah you're right there, I didn't really think of local coop at all, probably because I don't really like multiplayer that much so I usually stay way from it.
And the disability point is also correct and for that reason I'll be looking into a setting like this: "Accept input from all connected controllers", therefore allowing input from all controllers without selecting one from a list.
This probably won't magically make all those non-standard controllers work though.
I'll also be looking into adding that list to be able to select controller if the above setting is turned off, which it would be by default.
And using "Joy2Key" is an option I guess but I'd rather just have it work in game.
And finally, for your second edit, refer to the "button 9" part of this post, there is an issue with select apparently.
Anyway, I appreciate the feedback, I'll be trying to add these new features and fix the issues.