i recall playing many a game on that very cab (well not THAT one) and the control panel is indeed small..
even as a kid i remeber feeling my personal space being viol ated during 2 player games..
i dont think you are going to be packing in a whole bunch of controls into that panel..
i think you should probobly just ,and this is just my opinion of course, clean it up real nice and simply keep the 6 button 2 player config as is.. its a well respected title in a well modeled and attractive cab, youve nothing to be asham,ed of to warrant a full bore maming.. i recomend the stealth mame..
refurb the ewxterior to its original glory,hide a jpac, and a small PC and keep everything stock.
just my 2c