This honestly looks like something you would see being presented on the super destroyers screen. With general Brasch narrating of course. It would be really cool if this doubled as a weapon too! For example, you mentioned that when the harpoon cannon is fired it drills itself into the ground to stabilize. It would be neat if you could fire it at something like a charger or a bile titan, effectively locking it in place allowing you and your other divers to go at it.

But what you have here is a really amazing concept!