Sounds like a lot of work, but it'd be cool. For sure it's going to be a ton of work so it seems you may as well ditch the Bally MPU and go to something more modern, maybe watch some of Ben Heck's videos and see what he's using, and/or look at the Beaglebone, Raspberry PI or Arduino platforms. The amount of horsepower you'd have in the new micros would be overwhelmingly better and you'd get a modern development platform, and you would not need a ROM burner.
There's a Scott on RPG (seymour-shabow) that did/does programming on the old boards if you still want to do that, do a search for his posts and look for "Trident", I know he modded the code for that machine.
Send pics when you get started!