I build the 12-ESC board a while ago, and have been waiting on Ali Express to deliver the connector cables. Well, finally the arrived and I was able to laser cut the acrylic housing I'll use to pot the ESC board. The assembled board, in it's housing and support structure, with the connectors is shown below:

The top and bottom connectors attach the ESCs to their respective motors. The right connector is the ROV bus and will attach to the main pressure vessel. Later this box will be filled with QSil to keep the electronics safe.

The female connectors plug into the male connectors attached to the thrusters mounted on the frame. All the wires are connected using marine grade heat shrink. Again, the goal is to keep this modular and allow me to switch and replace pieces.