Hmmm... this seems to be turning less constructive and more just bashing the whole idea of the system.
Yeah, that's exactly what I went through when I recently asked about building a control panel. Bash bash bash useful-info bash bash info bash info. In the end, I heard enough info and went and built 3 control panels instead of the one that I originally envisioned. In the end the info I got was very good, but it was a chore.
Here's some lessons I learned going through this whole process:
Get some pieces of cardboard and do some mock-ups of the control panel design.
Get together with your buddy and check out the control panels, "playing" them to see if the buttons are the correct distance apart, etc.
This is especially important for the trackball to see if it has enough room.
Consider the underside of the joysticks, which can take up more room than you might think and may get in the way of button placement.
Ditto for the trackball, which is huge underneath.
This is also important to see if each player's set of control is far enough apart from the next player's set of controls. Four people around one game can be crowded.
Go buy 8 or 10 different buttons - Happ, Happ Super, Seimitsu, other brands - and set them into a board or piece of MDF. See what's involved.
Play with the buttons and see which brand/type you like.
And a joystick if you can afford it. It sucks to buy 40 buttons and 4 joysticks and THEN find out that you wish you had bought others.
Think about some other buttons that might be nice to have on the control panel, like ones for Pause and Exit.
Read all the controls' page on Ultimarc's site and be prepared to be surprised anyway.
Buy way more wire and crimps and cable management supplies than you think you might need. Two of us - very experienced computer & electronics guys - made 3 subsequent trips to buy more wiring stuff.
Cut, strip, crimp and tin the wires ahead of time. And cut the wires way too long. Then the control wiring itself will go much faster.
DO NOT finish the unit (ie; seal it up) until you have played the crap out of it. You will find flaky connections, loose wires and crimps, and microswitch prongs that need tweaking.
Do not be surprised by all the folks who think you are spending too much money and not being authentic enough. It's your cash and your fun.