The ecology idea is really awesome and also could imo provide very much depth (pun almost intended) for gameplay. Maybe the player can / even has to find out WHY some changes occurred? Or maybe mission goals could be to increase the population of a …
I have somewhat mixed feelings about procedurally generated content. So far subnautica's world is so lovingly crafted that I am a little worried that procedurally generated content could be too generic.
I certainly would prefer a borderless map over the neverending deep as it is now (but that's maybe only the cowardice talking in me; seriously this endless depth is creeping me out...)
Agreed, the map has to become bigger. For me persona…
How to implement it is, of course another pair of shoes ;-) But the game could for example start loading a part of the other side of the map when the player comes nearby the border.