How large are the ROMs? Do they require RAM? Battery? Special/other?
I made this, but haven't gotten around to producing any.
Spoiler warning:
I want to clean up the through hole placement and the silkscreen, but it should function for any ROM up to 64KBytes without populating the 315-5912. If you had that which can only be extracted from an official cart (right now) you could support ROMs up to 1MByte, but the ROM chip I placed is a measly 512KBytes.