For a CSB locomotive balance is important at least in reducing dipping and pitching at the ends of the chassis, i would avoid using CSB on a 0-4-0 for that very reason and go for compensation instead.
The final gear wheel could be removed easily. I can see multiple ways this could be used, for example secondary animation on a model such as boats on a river etc etc
There was usually one parked up in Reading depot on a saturday afternoon, i can also remember one ex works blue in 1971 going through Reading with a small train of milk tanks London bound also on a saturday.