Very nice explanation of things. Too bad you couldn't tie into the original switches. How catastrophic would a splice have been? It's just sending signal voltage right?
For the playfield, it's vinyl IIRC. How do you protect it? Is wax sufficient, do you have to do it more often because you have less material providing the color before you go down to the base color? Once it's down can it be cleared, or does that do something goofy?