Alot of people suggest that you add the prawn suit again but it seems old as it fits more to the older games. I noticed that the pilot cabin of the prawn suit looks similar to the tadpole. So why not combine them and instead add another frame with arms and storage? So that you can drill and brake resources the same way and move the same way, with the hook arm. Maybe you can change the looks of the arms so it fits the sub2 better.
The ‘prawn’ of this game is already confirmed to be a chassis for the tadpole, it’s called the bullfrog and is mention in the tadpole PDA entry.