2, 3 or 4 player support across 2 cabs or maybe be capable of linking 4 cabs?
Button remapping/configuration for the different setup via jumpers or dip switches, etc.
Kick harness connectors/integration/condenser for the different games/systems that need them
There are a lot of ideas but I don't want to get too far into scope creep.
Here's what I currently envision:
The "master" JAMMA passthrough will provide a 4-pin audio header, a 6-pin video header with an amp, and a 15 pin header for Player 2 controls
Then there is a wire bundle with 4 harnesses, a 4 pin harness for audio, a 6 pin harness for video, and 2x 15 pin harnesses for players.
Finally the "Slave" JAMMA board will look similar to that Konami board, it will have a 4-pin audio input connector, a 4-pin audio output connector, a 6-pin video input connector, and 2x 15 pin player input connectors. it will also have a load resistor. and maybe an LED.
This allows for the following:
1. AV connectors on the Pass through PCB and the player connectors directly on the game PCB means Players 1 and 2 on the "Master" cab and Players 3 and 4 on the "Slave" cab.
2. The P2 header on the "master" board allows you to plug in the player harness that would normally be for P3 and use this as a 2P VS setup.
3. the addition of the P2 header on the master board also means that for 3 player games you'll have the option of P1 on the master cab with 2 and 3 on the slave, or P1 and 2 on the master cab with P3 on the slave.
4. using a 4-pin header for Audio means that for those board that have a 4-pin stereo connector you can connect the audio to the original board connector as opposed to the master board. the addition of an audio output connector on the slave board means your slave cab can also get the full stereo signal instead of having to use the JAMMA edge.
5. with a video amp on the master board you can use just the AV connectors to output to a capture device
6. 3 players on 3 cabs using 2 kits: install 2 masters on the master cab, use the AV output and P2 header on one for cab 2, use the AV output and the game board player connector for cab 3.
7. 4 players on 4 cabs using 3 kits: same setup as the 3-players on 3 cabs except you install an additional master onto the P3 slave board.
Other "maybe" features:
-instead of using 15pin Konami style NH connector use TE-Amp Up connectors on the Master side with a short modular "pigtail" connector to convert to Konami style, or Capcom style, or Midway style, 4P connectors etc.
-include a jumper or a dip switch that swaps the coin and start buttons. There seems to be A LOT of these 4-player games that do not have a start button or a freeplay mode so this would allow you to use start as the coin drop for those games.
Things I'm not doing:
-Full button remapping seems overkill and would likely significantly increase the cost, I'm not sure how much value there is either since most of these games only use 2 buttons.
-a single unified harness. it might look cleaner to have a harness like the PGM one, but it loses all of it's modular functionality and hurts the feature set. Adapters to different style connectors would also be more difficult.
-kick harness condenser on the master board. not really necessary. most games with a kick connector are already using the Player 3/Player 4 headers on the game board for the kick buttons anyway. so this could be accomplished with using the P3/P4 connectors as is in most cases. I might include a CPS1 or CPS2 style kick connector on the slave, but it's more a matter of if there's room and how much cost it will add.