While that sense is a bit harder to maintain on a game the size of Atriarch, I think it can be done. I think one of the advantages of this huge world is that players will have more of an affinity for their home town, that regional communities will spring up. Some players will migrate, to see everything they can see, while I think others will be content to stay in one area and build relationships as well as the physical infastructure. You don't have to leave if you don't want to. It's that sense of community that makes online games so cool, but as the internet has gotten bigger much of that sense has been lost, I still think it can be revived however.
Most environments sound as if they draw influence from a portion of the Earth's ecosystem.
Expect an increase in the number of wolves in the area. Then the wolves will have to look elsewhere. It was a really neat system, but what they didn't account for was the effect the players would have on this nice balance. It wasn't long before everything was dead and there was nothing left to hunt. It wasn't Osi's fault, no-one had any idea how many players there would be or how quickly they could strip the forest bare.