IMO, just drill 2 new holes on each side to accommodate a 8way w/ 6 buttons setup for each player.
Fill the old holes by cutting sheet metal with tin snips, glue it with jb weild epoxy, fill it with jb wield putty & sand it smooth
Or just put another hole above the middle button, that may be a nice contour to yourhand when playing.
If you really want the spinner, trackball & a 4 way then you are going to have to do some cutting & reinforcing to the cabinet to hold a larger control panel.
contact flake, I think he had to cut & mod his cabinet for his arcadesrfun control panel.
By the way, don't always follow my advice either