If you buy a Pascal Janin all in one board you don't have to jack around with all those ground mods. The board is expensive but it really makes the game sing.
I'm finishing up a Pinball Pool. First System 1 game I've attempted. I've got it breathing pretty good now, using a donor board that I know has issues, but it's working now, which was more than it was doing when I got it. I've touched up the cab, repainted the glass frame, and got a NOS glass from Mayfair. Touched up and cleared the playfield, replaced all the drops, rebuilt the bumpers and flippers. It's going to be a nice game when it's done. I'm going to be getting the board for it it a few weeks.
You have to repin the connectors. If you don't you're wasting your time. If you're going to stay with the original setup, throw away the interconnect cables and buy new ones from Docent. No sense repinning those when you can buy new, and they're cheap.
I like Genie, despite the fact that it has those double flippers. Just never did like that flipper setup at all.