Hello,
This is Dan. I've been playing the game for about a year now and here is one of my suggestions.
The zombies in the game are barely a distraction and are way to easy to deal with for this to be a Zombie game. Especially when the meta is just to lock them up inside buildings.
It is clear that the number of zombies that spawn already depend on the size of the city. However, I think it would make for a much more immersive experience to increase the zombie population in bigger cities, as well as locations where military loot appears, to include INSIDE the buildings. I've never really seen zombies inside buildings (unless put there by other players) I find that hard to believe as people trying to survive would group together inside buildings before getting infected.
I understand that increasing zombie population would affect server performance, so this another possible alternative to making dealing with zombies a little more difficult.
Increasing the intelligence of the zombies by allowing them to break open doors and gates when they are locked in a building, as well as breaking down doors to get into a building where a survivor is hiding. This is much like the ability of survivors breaking down doors when they are locked in. Setting a certain amount of needed hits from zombies to open a door and continue to harass the survivors. This will most definitely make for a much more immersive experience.
I hope to see something like this in the game in the near future.
Thank you for making the game in the first place.
Dan