@darkpolletto your approach is ok here. I can confirm because I do similar on some of my machines. In my case I have the control panel wired to a set of female DB15 plugs and either use the JAMMA wiring from the cabinet terminated to a set of male DB15 ends for P1 & P2 or swap to a pad hacked console controller also terminated to male DB15 for when I want to connect a console to the cabinet.
The approach should be similar for superguns, assuming you plan to go that route instead of a full on arcade cabinet. Sounds like you are hacking together a JAMMA harness setup if I'm reading that right and if that's the case, then all you need to do is wire your digital control signals to the appropriate pinout for your intended control device or adapter. Add in the +5v signal for anything that might require it (undamned USB for example) or don't if you do not plan to utilize it. My console padhacks don't need it so I did not wire it in for my own setup. I also have some Neo Geo pads that function perfectly in this setup as I wired up the DB15 ends on the JAMMA side to the extended Neo Geo standard. It's a quick swap whenever I want to use that instead of the control panel.
Some additional things to consider:
- PSX / PS2 controls have more inputs than the 15 available that you can wire up natively with a DB15 setup. You'll need to either not use a few or wire the extra ones to some place outside of the JAMMA edge + kick harness if you intend to use all of those inputs somehow. Similar applies for newer consoles ie: PS3, PS4, Xbox variants, etc
- I can't speak to the nekotec converter you have pictured in one of your replies but before going that route you should confirm how many inputs are active and what the pinout actually is on that DB15 plug. There are some Neo Geo converters which do not carry more than 4 active action buttons, since 4 is the total available for Neo Geo. You might be better off in general to just wire up your own solution in this case.