Hi
I built a MAME cab (unfinished, but I got a long way through) with a 2-player layout, plus a central trackball.
But I *really* didn't like how it felt to be standing in front of the left hand side of the cab to play the 1980s single player games of my youth (Mr Do, PacMan, Donkey Kong, Frogger, Galaxian), instead of central to the monitor. And one of the first things my wife said when she fired up Galaga was "Why aren't the controls in the middle like I remember?" (instead of "great job, love that I can play Galaga just like I used to in the arcades").
There were also some other things about the cab the left me dissatisfied - but the position of the controls for a one player game really irked me. So much so that I've scrapped that cabinet and started a new one that will have removable panels for 1 and 2 player.
I'm sure a lot of people would be fine with one player games on a two player panel (and I certainly thought I would be), and it would have been different if my panel didn't have the central trackball pushing the player one and player two controls even further away from centre.
Martin