I wouldn't anticipate anything like the blast-off in the video.
Agreed. The so-called "blast off" is not typical and, I strongly suspect, was done purely for dramatic visual effect.
... the thrusters had to propel the entire weight of the submersible up off the bottom.
Actually, I can't agree with you there. Remember that a submersible in the water column doesn't operate like a helicopter or a Harrier jump jet in the atmosphere. It is more akin to an (extremely maneuverable) airship in that the pilot can trim ballast so the vehicle "weighs" less than two ounces .. or even so it becomes positively buoyant. A full power thrust is not at all necessary to heave its bulk off the bottom, but it sure looks cool on camera. I'm certain the spot near the Japanese midget sub wreck was carefully chosen and the shot staged so as not to disturb the artifact.
The real time presence of live eyes and brains aboard the HOVs (Human Occupied Vehicles) is a major advantage that means anything "interesting" can be spotted more reliably and investigated immediately. Plus, the wide field of view, powerful lighting, and precision control afforded by the
Pisces subs will allow for a more prudent and considered exploration of whatever promising targets are detected.