maybe it is possible that a group of players can build a base camp.
There you can place tents , cars, all the loot, etc. (maybe even sink a well there)
It should be possible to build something like a fence around it and
can be locked up with a padlock or combination lock, that not everybody
can easily enter the base camp. All the things, that are needed to build the
fence, gate and lock etc. can be found somewhere (it should need a long
time to build up a base camp).
This maybe can cause, that some players estblish an alliance against other
players ...
so you frist start to survive in a world full of zombies an by time you build up
a "enclave" that you need to protect from enemy-alliance and zombies .