Having an invincible RoboCop would be a devious punishment for arcade operators bootlegging the game. One quarter would eat up a lot of time on the machine. It would be hard to make any money on it.
So that means there are 2 ways to crack it. Emulate both CPUs, or rewrite the code from the sub CPU to work on the main CPU.
Personally thinking, I need to buy a breadboard and start tinkering.
His track "Eon" here is from a very famous and artistically beautiful demo. https://hoffman.bandcamp.com/album/the-cave-sessions