I’ve run into a couple limitations of the game controller API when working on a new controller mapping UI for my Genesis/MD emulator, BlastEm. In particular, I’m looking for button labels that match the device and identification of controllers with non-standard physical layouts like the various fighting pads. I can certainly implement those things myself, but I imagine I’m not the only person who could use that. Indeed, I found this thread from about a year and a half ago that mentions the button label issue.
I’d be willing to spend some time working on some patches if there’s interest.