Hey there. This game (intentionally or not) is already compatible with over 400 controllers, because if you take the keyboard and mouse defaults, and plug them into JoyToKey, the game won't conflict with the created layout. It's also possible to split the keyboard and mouse defaults across multiple controllers, and make the game a 2-player co-op.
I wasn't able to figure out what was causing me to run into pill upgrade opportunities.
I would love to see a Windows version.