You got it - or at least part of it. :-)
If this is just part of it I look forward to hearing your concepts fleshed out further in a Dev Journal sometime.
Is it possible that if the population of some mobs increase too much they will wander in search of another place where to put their new nest? And if the mobs are intellingent type (ogres or goblins) they will be able to assault caravans and/or villages to gather some food (maybe human flesh)? There will be some kind of public event in these cases? That aim to get as many PG as possible to drive away the mobs?
What about the other side of the coin?
What if the PCs put so much time in hunting and killing mobs that all the really scary monsters never develop into supper mobs?
Sounds like that world would be boring to players who want to slay monsters. Hopefully there's a system for nature to "react" to, not imbalances, but depletions like this.
How strong will the AI be in this game too? In ESO you can't even hurt the guards even with a mob of players will it be unbalanced like that as well in the cities.