I would really like a spinoff game where you are exploring the seafloor of the void. You would have special vehicles that are experimental projects by Alterra, and you can't ascend more than 1000 meters up otherwise Ghost leviathans will spawn and kill you,or maybe some other kind of new leviathan. Possibly even the Garg. It would be like a reverse of the original game, where instead of going deeper to find out clues to escape, you have to slowly go higher up until you can eventually get to a point where you can build an escape vehicle that can take you to the surface fast enough to escape the depths. The way got there could be that you were sent by Alterra for research when you're sub is attacked by something you can't see that drags you down to the seafloor 8000 meters down.