Bengaz:
I assume that you'll be playing around with the spacing, putting the diagonal cutouts on the front of the panel instead of the back, and putting all the joysticks to the left of the associated player buttons.
One thing that I noticed is that you don't have Escape (exit), Enter (select), or Tab (menu) buttons or coin buttons for players 2, 3, or 4.
Is that 3 pairs of mouse buttons?
The biggest danger that I see is that in trying make a panel to "play all the MAME games" you could VERY easily end up with the dreaded "Frankenpanel".
Start with the list of games you
definitely want and add the controls that they call for.
Spend some time reviewing the
Hall of Fame thread for design ideas and take notes on what you like. Ask yourself, "Why did they do it that way?"
The time you spend on design now will be time and money saved when you are happily playing a well designed panel instead of being all
because you can't stand the layout and wonder why you wasted the $$$ and effort on making it 4-player instead of using a couple of USB gamepads for the 3 times in the last 2 years that you've actually used player 3 and 4.
One-panel-plays-all is impossible, but one-panel-plays-almost-all-of-what-I-want is definitely attainable.
Scott