Reverse Engineering Mayflash PCB "MF002V"

This is a pretty nice little PCB that comes in the Venom Arcade Stick PS4, and has two daughter boards: MF-JOYSTICK001-KEY handles four push buttons and three switches, each switch with an on and an off position. MF-JOYSTICK001-LED handles up to six LEDs (player lights 1-4 and a turbo LED, as well as a macro LED which isn’t used or populated in the Venom Stick).

In theory, the -LED and -KEY daughter boards are probably used in any stick with this mold, although the Mayflash F300 and Arcade Fighting Stick for Xbox360 / PS3 / PC almost certainly use different PCBs for their main board (no native PS4 functionality).

It’s a nice PCB! But by working out the pin-out for the two daughter PCBs, we can either replace it with a Brook Universal PCB or another one - say, PS360+. I can’t find any information on this, though.

I’m trying to reverse engineer this PCB using my limited skills - I’m using modified ribbon cables to try and work out what pins access which features. Am I right in assuming that the ground pin will be the pin which causes the entire board to stop working when disconnected?

Alright, assuming I found the ground correctly (and from what I know about circuits, I’m sure I did, this is the pinout of the top-left daughterboard on the Venom stick:

I’d like to do the lights next but I don’t have six PS3 controllers to make sure I’ve done it right - is there any kind of a test program I can use?

Hopefully this makes it easier for Venom owners to do full PCB replacements and make these sticks into the multi-system beasts they deserve too be!