Extended JAMMA pinouts are needed by more than just Neo-Geo.
Even Taito's official JAMMA kit places buttons 4 and 5 on the JAMMA edge, only using a external connector for button 6.
This is why I love both the HAS and the RECO!
For me RECO acts as a button consolidator, allowing my cab to feed 4 and 5 on edge but then moving these back to a common CPS2 style connector.
The only problem is they are bridged, active on both the kick harness and JAMMA edge at the same time.
If it was selectable via a switch you could decide based on the game boards requirements.
Need 4 on the edge for Neo-Geo? Just move the switch over to say "JAMMA" if you need 4 on the kick harness move it over to say "CPS2/3".
I blame Capcom for this honestly, if they released "proper" code it wouldn't look for the buttons in both places.
It SHOULD totally disregard JAMMA pins 4/5/6 and I believe that WAS the original intention.
As other games like Super Street Fighter 2 Turbo are completely unaffected by this edge+harness issue.
@RGB is actually right to suggest the change to the ROM and not the hardware, only problem with this is the encrypted ROMs we are all running now thanks to key writing firmware.
If it wasn't for the D&D games, I'd just cut the JAMMA traces on the CPS2 A-board leading to buttons 4/5.
Who knows I still might, I don't have a 4-player cab so fuck it (you messed up Capcom and now your hardware WILL get hackedup as a result).
