Remember Mr. Newton. That 150 cu ft tank is really heavy, and will take alot of thrust to get moving, and alot again to stop, turn, etc.
I bought 3/8" wall, 8" dia, 4' long aluminum pipe from onlinemetals.com , cut and welded rings on either end. Then i used a dished aluminum end cap for the back end, with all my penetrators going through, and a 1/2" wall 8" acrylic hemisphere i had custom-blown from
https://plastic-domes-spheres.com/ . My thruster ESC heat sinks were reshaped and are spring-pressed against the inside curve of the aluminum pipe, keeping them cool. I have two more pipes with 12vdc 10ah SLA batteries inside, series to 24v, pararell to 200ah. I am in the process of building new packs with Li-iron-phosphate batteries. Since my ROV is the size of a 10 cu ft chest freezer, i used brushless drills (handles cut off, body filled with mineral oil) turning 8" symmetrical aluminum ducted props as thrusters. Bearings are replaced with ceramic, stator/magnets coated with thinned epoxy resin.
I put a 78x optical zoom Panasonic SDR-T55 camcorder (used on eBay for aprox $50) on a pan-tilt gimbal inside the dome. I use a servo to move the zoom toggle. The composite video out goes to an 8-camera security-system DVR board inside the WTC (water-tight-container). That is connected to an ethernet switch, which is then connected to the eKL ethernet over coax unit. The ROV controller is also connected through the switch. I potted cheap $16 Eachine FPV microcams in clear casting epoxy, they mount externally and give me views in all directions.
I built two 9-dof manipulators (driven by regular metal-gear servos filled with mineral oil to keep the water out while taking the pressure at depth) so i could grab stuff. Because one camera gives no depth perception, i have microcams mounted on each manipulator's wrist, so I can look back and forth between screens and judge grab angles. Inside the dark pontoon boat cabin i have a cheap $100 1080p led projector displaying the 8 camera feeds onto a 120" screen.
I have a homemade headtracker on a headband so when i move my head, the Panasonic camera follows my head movements. Two Virpil Constellation Alpha joysticks (3D printed and DIY) connected to multi-axis gimbals allow control of the manipulators. The joysticks are suspended from the ceiling by dacron line with counterweights to reduce arm fatigue.
My original control interface was a Raspberry Pi 3B with a Pixhawk controller (Blue Robotics), but i am in the process of upgrading to their new Navigator Flight Controller.