This would be a relatively modular build, but the machine would need to be modified to allow balls to feed into the launching system. Having a powerful actuator/spring like a pinball machine, and a stepper motor to change the shot angle would be easy (hah) , and the scoring would already be handled by the machine.
Ideally the queue for the balls would run all the way into the launcher as they were released by the game, so either modify the track so that it runs up and out, or open the front or side of the machine to allow them to move all the way into the launcher. This might challenge some of the goals of the project which seem to be keeping the equipment looking original and unmodified on the surface. Maybe dropping the ball down through the bottom of the feed/hopper would be more desirable, but more complex.