This is a game changer
I wonder if the following has been thought about.
Enemy sub owning country (ESOC) is a bit upset at this new capability. In the past eg during cold war, brinkmanship was the name of the game but in general, threats were made but no or minimal action was taken and certainly lives were not taken if it could be avoided. That simplifies things somewhat but these drone thingies have no people aboard or if they do then they are no longer drones.
ESOC arranges for a rock to appear under the water line in the Atlantic/Pacific. Shame but no person was killed so not a problem. Many drones start hitting "rocks" or whales or something and sink with no hands but the public don't care.
So you put people aboard and make ESOC well aware of the fact. Your drones stop sinking for odd reasons but you no longer have properly autonomous drones and you have to keep the baby sitters happy and they want to control the thing and they insist on eating and having water and/or booze and time ashore and so on.
Never mind, your drone contractors have a healthy profit margin and very happy shareholders. Lovely.