ben heck did a teardown and convertered one to handheld. You will likely find some interesting tidbits in the breakdown.
My plan is the following ; Pull the PCB and CP out. I'll then build a semi-custom enclosure where the mini HDMI / USB 2P / USB C Power IN come out the back for hookup.
I'll solder in leads to the underside of the CP on U/D/L/R and Ground chain a wire in. Those will terminate to quick disconnects, and into an actual arcade stick. I'll hit the test pads on A/B/C/D w some solder and toss in some quick disconnects as well to go to four arcade buttons. Same deal w/ start and select.
I'll mount the CP and PCB into the enclosure, and drill holes for the buttons and stick.
If using the pot solder points work (10K put, set high, so as long as the circuit off the stick pushed 10K or more to complete a signal) I'll have the guts of the Mini in an enclosure with a fully working arcade stick setup.
Why? I have no idea. I am bored and it seems fun. I could literally just hook up my AES and play this shit but...one more project can't hurt lol
Basically it will be a 1P "Pandora's Box" style setup w/ the guts inside the stick, except a Neo Geo Mini w/ legit arcade controls.