Even though most of the population has become zombified already, I assume at the start of the game there are still some stragglers. These are mostly intended to be zombie fodder, so unless they are getting a really lucky spawn they will die quickly.
Idea for a microfactions:
A police station with one (or more?) officers left, mildly fortified with boarded-up windows and similar. The officer still has 2 prisoners in the holding cell and will not free them (because “Justice”) and thinks the whole Cataclysm will be over soon, with reinforcements already on their way. Needless to say, the stubborn officer means death to not only him but also the prisoners.
However, if they manage to not die, they could have a quest where you could kill-off the officer and the prisoners become your allies. Alternatively, you could side with the officer who wants you to acquire a prison bus so “Justice” will finally be delivered.
A fortified house with a basement, home to the zombie hunter microfaction. This little group of about 5-6 survivors banded together to try and end the Cataclysm by hunting zombies. Needless to say, they will soon be outnumbered and killed off because the likelyhood that they spawn near crowded areas is high.
If they do not immediately die though, you could try to persuade them to join either Tacoma or the refugee center. Perhaps either by social skills/persuading or by obtaining an agreement from either the Tacoma or refugee center leaders.
Lone NPCs with no particular backstory, I assume their locations could be altered to be fortified a bit so their death will be delayed, even if just a little, but them dying is still highly likely:
- A lone restaurant with a cook who wants to complete one last delivery.
- A park ranger on top of a fire lookout tower.
- A rando in a dermatik nest, requiring immediate medical attention, might beg the player to just kill him off.
- Some cocooned (idk how to implement that, treat it as a vague idea for now), severely weakened NPCs in a house turned into a spider nest.
- A car crash victim.
Basically some professions the player could choose, spawned ingame as NPCs. So there is no NPC overload ingame, most of them should die pretty quickly.