Hey, just a comment about your fab process. I am wondering if you want to bother soldering the EPROMs yourself. If you are having the boards fabricated, for the sake of time and cost, maybe you can also get the fab house to solder on a blank EPROM, which means you won't be limited to what SMD technique you can do yourself (plcc, tqp etc), ...maybe you can order a BGA or similar which would make for a low profile cart? Then, to program it yourself (even though the fab company could also do this) you just need to make a female cart slot to EPROM programmer adapter board, and just run the completed carts through one by one to program them, then ship.
I prototype a lot of stuff myself, and I think this is something I would investigate, worthwhile to do a time vs cost study etc. More time for software development