I know someone is going to say this needs to be added to contorls.dat

I think you are making it a bigger problem than it is.
First, most games if they have buttons on both sides of the tball, joystick, whatever, were designed to be played both left handed and right handed. For example, if a game had a joystick, 4 buttons, 2 on each side it probably is a game that only uses 2 buttons, the buttons are wired together.
You will find there is a game that is an exception to everything you come up with. In this case golden tee golf would be the exception.
Second, the layout isn't really an issue. If you aren't looking at other control panels when you design yours you are going at it wrong. Plus if a game had a specific layout and the person is a fan of the game that person will know the layout and design for it. Someone who hasn't played a game before with a different layout will probably not design something for that particulat game. For example if someone hasn't played asteroids on a real asteroids cabinet that person will probably not layout buttons that way.
Plus, how can you document specific layouts? The only good way is with pictures. So then do a quick search on google and you will end up
http://www.mameworld.net/mrdo/mamepanel.htmlMAWS is only as good as the information it gets from mame. If they sould include info from controls.dat the accuracy would improve. The big reason controls.dat exists, see dotron at maws...