I once read a book called (I think) Richard Marcinko the Rogue Warrior, Navy SEAL CDR. The author claimed to have been hired by the government to “test” Naval security. Much to the embarressment of his “employers” he claimed to have successfully infiltrated numerous Naval vessels. If true, it raises a valid question. Could “bad guys” exploit aft steering/auxillary control to take over a major Naval vessel. My guess is NO at sea, at least with regard to an aircraft carrier. However, at Port might be a different matter. Also smaller vessels might be more vulnerable even while underway.
On smaller vessels it would be at the same time easier to notice something/one that doesn’t belong there. But aft steering alone would give you limited abilities – if you don’t also take over the engine room, the lawful command can just immobilize it while they storm your area; if you dont take over the radar/radio room you’re deaf and blind, if you don’t take over fire control you’re just a sitting target.
See, that’s what I was talking about earlier. Control (not the same thing as command) of a naval vessel does not reside in one compartment; it’s distributed all over the ship. You would need a large, well trained team to take over a warship. One man would not be capable.
I believe that, in confined waters, it might not be too difficult for one armed man to take over the helm and run the ship aground, into the docks, or (with more difficulty) collision with another ship. Maybe on a ship the size of the Nimtz the bridge crew is too large for that, maybe not. If you kill or capture bother the captain and Office of the Deck and lock the hatches (I don’t know, can naval hatches be locked rather than just sealed?), you have maybe quite a few minutes before someone realizes the commanders aren’t in a position to command, and takes countermeasures. Not really what the OP was asking, but it seems feasible.
the aft steering compartment is for emergency steering. If there is a loss of power to the bridge, the ship can be steered for here, usually by direction from the bridge (as you couldn’t see anything from in there) via VHF radio. I’ve steered this was many times. Captain or mate at the magnetic compass, helmsman in the steering room. It’s manditory, I believe, to test your gear this way on a regular basis. It also overrides the bridge console steering because if you’re steering on autopilot and your gyro compass screws up, you’re in for some serious trouble.