LEM

I'm using the JPAC from Ultimarc. It allows you to remap buttons and also has a shift function when pressing the 1-PLAYER start button. If you don't have a JAMMA interface, you could use the IPAC instead from the same company.

I grew up in the 70s/80s and spent all my childhood in arcade saloons, and I find horrendous the control panels that people create nowadays with so many buttons. In my case, I can achieve the same functionality having one button that works as an SHIFT key so I can have the same button with 2 functions. I use the 1-PLAYER start for this. This is my panel. I have also added 2 small on/off buttons that you can see in the image. One to turn on and off the cabinet and one as an ESC key. In my case I have 3 buttons per player. I would add 6 if you want to play fighting games. For me it is good enough like that.