Hunters- a group of people dedicated to clearing out all zombies in sight.
A well stocked group- a group that has more supplies than it needs and are willing to trade/give you supplies in return to helping them survive and saving them. They could give you missions in exchange for supplies. (I know that's basically what there is now but I'm thinking on a larger scale and you can choose whatever supplies you need.) Or maybe they're specific to one particular supply. (Ex: they're farmers so they only have food to give you)
Another group like red talon or the network- maybe like a military group or some sort of militia. Something on a smaller scale than red talon or the network. They only have one base but they're heavily armed and well stocked.
You can work with these communities and trade goods and could recruit them. maybe they have an actual base and you could go there and see there progress. I feel like that could bring a little more realism to the game.