Frank_fjs, creator of the Sentinel supergun, just designed a board that works jointly with the Digital AV Interface announced/designed a while back by Markus Hiienkari of OSSC fame.
The Helper PCB mainly provides 2 Neo-Geo controller ports and power connectivity, basically eliminating the need for a supergun for a comprehensive CPS2 setup.
Here are the specific features, listed by Frank_fjs, about his newly designed board:
– JST VH connector for power, connection to arcade PSU.
– JST XH connector for the kick harness.
– Dipswitch to enable/disable buttons 4,5,6 from the jamma edge.
– Test and service tactile switches.
– Two Neo-Geo controller connectors with Undamned pinout.
There is no plan of manufacturing/selling the Helper PCB as of yet, but Frank_fjs has made the design files readily available for download.
Check out the official thread here: https://www.arcade-projects.com/forums/index.php?thread/7769-cps2-cps3-digital-av-interface-helper-pcb/
EDIT: HAS creator RGB also has a similar project: