"Ah, I was hoping that this would replace the mainboard altogether. What then is the advantage of the JAMMA board you are making as opposed to the standard JAMMA board for a game?"
Yes, it will replace the original main board, all that is required is the Replay board and it's Jamma adapter. For example, if you want to run the pacman game you need the FPGA core which behaves like the original hardware and the ROMs which contain the software.
I'm also doing a vector output for games such a Asteroids.
Mike