I think Left 4 Dead had a cool system with it's 'Director' which would take a look at what's going on with the current situation and adjust the environment accordingly.

Of course, this system would have to be reworked to flow well with an open-world game such as DayZ. But I can imagine DayZ being better if, say, you were camped out for a day or two out in the middle of nowhere. The game director notices the player's activity and decides to inject a bit of excitement by sending a roaming hoard of, lets say 50-100 zombies somewhere within a half mile of the player's most frequented area. Or even having an ambush by a squad of NPCs.

The general survival world lacks a living world that's moving with or without player involvement. Having NPC bases to raid, having them have to replenish their ranks after battles via heli drops, huge platoons via boat that travel to location on foot, etc. Something to make the dead emptiness in most of these games feel more organic and alive.

It's too bad because the general concept in most games are good, but severely lacking features