"Things like a secondary power and/or propulsion source, or a backup means of communicating with another vessel or the surface, should be the minimum safety for a deep-sea diving vessel such as this."
I read that normally on these types of deep sea mini subs subs, the ballast (weights) that allow the vessel to sink to the ocean floor are held in place on the bottom of the sub with electro-magnets, so in the event of power loss, the magnets shut off, the ballast automatically drops and the ship ascends back to the surface. Since they are on the bottom, this works even if you're sitting on the ocean floor. Sounds like a pretty clever way to do things.
However on the lost sub: "the ballast is abandoned construction pipes that are sitting on shelves
on the side of the thing, and the way you detach the ballast is you get
everybody on-board to lean to one side of the sub and they roll off"
The problem with this is obvious. If you're sitting flat on the ocean floor with no power, you're not gonna be able to rock the sub side to side to have the ballast roll off. Seems like in addition to all the other questionable design decisions, just learning that this is your method of getting back home would cause any potential passengers to say 'oh hell no'.