I will be following this for ideas. I have an old arcade cabinet, and have been toying with the idea of making a mame cabinet myself. Never thought of using vslot, but I think it is a great idea, will make mounting things in the wood cabinet a lot easier and more professinal looking.
I really want to recommend Pimoroni's Picade PCB. It's basically a USB keyboard device, with screw terminals for a joystick and 12 buttons. It really works well for me. Right now, I just have everything in a box, which I use with my laptop. It's only one joystick, so I've ordered a second for this project, but I didn't need any drivers or anything to make it be go. They also have picade hat, but since its one joystick, and only works with the pi, I didn't think it was as flexible and didn't want to be locked into the Pi, either.