Have you played around with offseting the center column upwards in the six button layout? I did this for my desktop panel, and I love it.
As to critiquing, you really need to print out some scale button layouts and see what everyone that will be playing this machine thinks. you dont have to build a cardboard model just yet. Just set some layouts on the kitchen table and get some input.
I originally planned a monster of all monsters frankenpanel when I first got into this hobby. So does everyone...that is why there are so many examples of machines with 5' wide control panels, and a 19" monitor.

Take a step back, get some arcade parts to play around with, and make sure to build what you really want, not just throw every part you see onto a panel. You don't HAVE to have one of every control. You also don't have to play every single arcade game ever made. Another thing I have done is actually work my way thru the entire game list to figure out what I really like, and what plain just sucks. You learn alot about what controls you really want and need once you have played them all at least once.

That will be 2 cents please.
