I can't decide what I personally think is better in regards to zombie counts in the world.On one side, a ton of zombies would be impressive and a lot of fun. On the other side, if it was like that all the time, there would be no surprises and being surprised is fun too.
I imagine trying to loot a POI with a ton of zombies outside being a challenge, which is good. It might take all day.
However, when I go home and come back the next day, I wouldn't want to do the same thing all over again just to hit the POI next door.
That would get old real fast.
I would probably do something like a reversed heat map for cities. I'll just call it a cool map for easier reference. At first a ton of zombies can spawn in city chunks because the cool map is high. The more you kill in a chunk, the lower the cool map goes. If you happen to come back the next day, those chunks probably won't trigger spawns. After a couple, maybe a few would. If you haven't come back in over a week, the cool map would be at max again and large groups spawn in those city chunks again.
I am pretty sure the encounter system will solve a lot of this, but I can't help but think that it will feel gamey.
For example, the digging quests. The zombies that show up the instant you empty the chest is a cool idea... clever the first time, not so much after that. It's actually funny to try to grab it and look around to watch them pop in. The yellow paper challenge notes that bring you to some location in the wild where you can watch zombies pop in seems even gamier. I don't get a good feeling playing the game during these moments.