Alrighty...thanks to all of your insight, I have been able to narrow down how I might go about constructing this control panel. Basically, if I hack a PSX controller to my control panel, that would leave the PSX connection to do what I want with it. I know that there is a cheap adapter to plug a PSX controller into a Gamecube port. There is also a PSX to USB adapter that is a bit more expensive. My question now is how do I plug both of these in at the same time? Is there a way I can split the controller to go to both inputs? Also, what kind of PSX contoller should I hack to do this? Should I be trying to hack a PS2 controller instead? What about analog? I would prefer to have the plugs connected to both the computer and the gamecube all the time, without having to change them constantly. Also, any suggestions on how to connect both pc and gamecube up to the monitor? Better yet, how can I easily switch between the two of them?
Phew...lots of questions!! Sorry about that, but I'm not the foremost authority on any of this, and I could really use the help. I would love to hear from anybody who has a cabinet with multi-systems, as well. Thanks for listening! Hope to hear from you soon.