At this stage, your old CPU board can still be saved if you remove that Varta backup battery asap. Notice also the burnt 3V zenerdiode in the undervoltage protection which is a design error.....

Removing a battery won't cost you a $ assuming you own a solder iron. If you leave it there for some time you can throw it away for sure. If you remove it might be usefull as a spare or sell it for some $. Just a thought. It is your board of course.

You are telling us the knocker and flashers are locked on. Is the game coming to attract mode, i.e. displays coming up, controlled illumination is running?

Bad Girls is one of the fewer games which are running a 2732 in PROM2 socket. Is the Swemmer board configured like that? Most of the games are running a 2716 in PROM2 socket.

Your old board was affected by a leaking battery.....the 4 pin power connector at the cpu might be damaged and if so, it has to be repinned. Same counts for the switchmatrix J6 connector.

The 5V power supplies are usually fine. Just tighten the screws for the LM338 regulator, replace and adjust the 500 Ohm pot for a sealed multiturn and reflow the header pins and it should last for years again.

If the so called "ground updates" are executed: DO NOT use the heatsink form the 5V power supply as a Ground Plane as it is barely isolated from the +5V (which is present at the case of the LM338 regulator).

Your CPU is not booting. The light strip is controlled by an independent aux lampdriverboard. This means there is +5V. But it is a good idea to measure if the +5V is landing at the CPU board by measuring it over the 100uF cap and eventually adjust it if it is low.

Check the setting for game PROM2. By default it is probably set for a 2716 Eprom. For Bad Girls it needs to be set for using a 2732 Eprom. Ask Fred Swemmer how to jumper it like that or check for info on the silkscreen at the board, I never used these replacement boards.