Profiting from the system by being employed there? That's not what I had in mind.

There are many opportunities outside of prison guard unions for innovation regarding the overall institution/process of incarceration in America.

Domain expertise will only be built by tackling a problem in that domain. How could one possibly decide against pursuing a topic without trying it at all?

Tough, seemingly entrenched markets often prove to be the most interesting: SpaceX, Uber etc