I had the idea of putting a raspberry pi a+ in a Namco plug and play game (one of these: http://i.ebayimg.com/00/s/MTIwMFgxNjAw/z/4iAAAOSwxYxUyENC/$_35.JPG) to turn it into a mini mame cabinet that you can put any arcade games on. You could use the existing buttons and joystick and wire them to the gpio.