Hello Bob, I’m very happy to see this post. Thank you for the detailed explanation of your situation and questions.
I am the maintainer of the ArduSub project, and I would be happy to help you accomplish your goals with ArduSub.
I have a few questions to begin with:
ArduSub does not support RC transmitter input (and I do not feel inclined to add it, due to it’s limited usefulness in ArduSub applications thus far). Would this be a hard requirement for the project to be useful to you?
Another related question, are you interested in tethering your submarines to provide live video and telemetry to the top?
ArduSub supports control of servos, relays, and brushed/brushless motor controllers, as well as a variety of sensors, and stabilization control. You are correct in your observation that ArduSub does not explicitly support forward-moving craft like submarines and torpedo-style AUVs that use control surfaces for maneuvering. This has been on my wishlist for some time, and it is a feature I want to have. I believe it will be possible to hack around and make it work with minimal modifications to the firmware, or perhaps even without any software changes.
Depth control via pressure sensor manipulation of the ballast system and/or forward dive planes
Sure, should work out of the box I think.
Bottom collision avoidance via depth sounder (in development?)
In development, but working.
Object collision avoidance via scanning sonar (in development?)
This will be a more complicated task that has not been worked on with ArduSub to my knowledge, but yes doable and desirable.
Autopilot Information and data relay back to operator during operation (heading, depth, speed, battery condition, etc)
You will need a tether like the fathom slim:
https://www.bluerobotics.com/store/cables/cab-nbpuf-1utp-26awg/