I'll be showcasing the "Multi-Bally" at TPF '19. (And possibly at HAAG '18.) I should be starting the build thread in a month or two. It will play MOST Bally games and SOME Stern games from the early S/S era. Meanwhile, Gerry and the guys at Multi-Morphic are on point with the many games, one cab concept. And you would be surprised how different one machine can be from the next. Stern seems to be searching for the next better system and it will make for incompatibility issues. Good luck!
Shawn