To my extreme dismay... Wasn't the board connector part of the issue?Like we would be required to sac a real Naomi cart at minimum (perhaps even a specific one like Melty Blood for a larger/more flexible address/load space)?
No, as twistedsymphony said, it is an OMRON XH3 connector:
Converting GDROM NAOMI games to cart.
As Brizzo says, the parts costs for an M4 cartridge may make that path uneconomical:
Converting GDROM NAOMI games to cart.
The controller required to interface the cartridge is the problem here. Each cartridge is controlled similar to a IDE block device.
There is a simpler cartridge type, that could be manufactured cheaper:
Converting GDROM NAOMI games to cart.
Unfortunately the bus connection for that is not documented properly, yet. Somebody on the assembler forum traced the connections from the motherboard, but you need to know how they actually connect to the chips on the cartridge.
I've got a derby owners club, which is a later cartridge. I was planning to crack it open to check if anything is connected to the unknown bus, but so far didn't have time. I'll have to take the connectors apart, which is apparently a fiddly procedure.
One option would be a daughter board that slots into the IC22 socket, and which grabs the higher address lines from the other footprints. You could then use the controller of the original cartridge, and connect to a dumb memory-only board.