Exactly. Making the controls yourself isn't necessarily better, as long as the rudders and engines are engineered properly. Some seperate (emergency) control might be a good idea, in case the Bluetooth fails. Just to get the submarine back to the surface.

The submarine is a one-off experimental one that isn't certified, hasn't been used a lot and dives deeper than almost any other submarine. That's enough alarm bells for me. Whatever they use to control the vessel is irrelevant to me.