OK, but Rudeism has beaten Dark Souls using a bunch of bananas as a controller (or something like that), so no surprises there.

Honestly, anything that says "We turned this into a working controller" is old news. You can buy a basic hardwired controller board off of aliexpress for practically nothing, and anyone remotely handy should be able to figure out how to wire it up. And if you want to do something more complicated like analog control and bluetooth, there's generic arduino libraries that you can combine with any number of compatible boards if you've got a bit more know-how.