Why not just use the original controller you ripped apart? Cool project but seems like a waste. I made my own controller/ fight stick for switch using an Arduino, and even uploaded my code here on a forum.
Generally most of the "let's cram stuff into other stuff" projects are learning experiences, they're not meant to result in an actually useful product. But you learn a lot.
I made myself a soundboard handheld w amplified speaker and 3d printed a case with 10 buttons. Loaded it with bird sounds. I sit on my porch alot and use it to talk to the birds, and they respond back to it. I think its cool but wifey thinks I'm crazy.