I've designed a PCB to mount the original Gamecube power switch to, and added a JST header for connecting to the motherboard.
I then worked on integrating the mount for it onto the motherboard standoffs, and figured I'd add an intake fan while I was at it. The fan shown below is a 60mm, but I ended up using a 50mm in the end to save space. The 60mm would interfere with the USB header on the motherboard and make it nearly impossible to plug anything in.
I also made a few modifications to the bottom shell, adding cutouts for the front I/O and a much sturdier slot for the front panel to drop into.