Who else thinks that the zombies should roam around the world (not just in towns) and gather into hordes, growing bigger as time goes by.
the reason i suggest this is because if you think about it, besides other survivors, the country side is rather safe. I'v roamed the forests and plains of chernarus for countless hours, never running into a single zombie, iv run into other survivors, sure, but even that is quite rare.
Imagine how much more intense the experience would be if you were running through the woods, and all the sudden you see a horde of 30-40 zombies migrating in front of you. It would add a sense of danger while traveling.
and it wouldn't be like groups spawning together, then traveling, but rather start with a single zombie, and as it moves from area to area, looking for food, other zombies start to follow it.
or say there was a firefight in a town, well, zombies naturally would migrate towards the gunshots, increasing in numbers the closer they get.

Im sure it wouldn't be an easy task (or would it? im not a game developer)
but it would increase the tense atmosphere of the game, instead of only worrying about survivors when travelling, you would also have to worry about running into hordes, which would range anywhere from 5 zombies, to 50 zombies, depending on how long it was been forming.

just a quick thought i figured id share with the community =)

p.s. wasnt sure where to post this, seen some suggestion on this section so i decided to write it here. if its in the wrong area, feel free to move.