Love love love it, been thinking of this a long time.
I want to go into a lot more detail, but that is more worth it’s own thing.
So, to sum it up. Things spawn in groups, and each group is assigned a lethality number (the highest and minimum). On a overmap scale, the groups as a whole is assigned it’s traits, and for NPCs, knowledge and personality. If a NPC group grows big enough, it makes a faction, which has smaller groups.
As the game progresses, certain groups tend to not spawn. With NPCs, the spawn rate lowers, but the size and/or strength grows. Only when individuals of the group spawned in, does the group divide the lethality, resistance, and defensive numbers to each part of the group.
So, in this system, if you at 20 years, and run into a single traveler, don’t mess with him.
Plus to the fact, machines should become more and more of a non-threat as the time goes on, since no one would be maintaining them, and the facilities they would have been maintained autonomously, would break down and stop working. Robots and AIs are an early game threat, but gradually fade.
And acid. Melting objects is unrealistic, particularly objects that are made to resist corrosion. Acid in general wouldn’t be viable from a zombie to use as a weapon, unless it produces mucus, thus be protected from stomach grade acid. At that lvl, it would burn, and long exposer would result in equivalent to digestion. Acid hurts, but it would be far from lethal, and if the acid spitter had a grade of acid stronger than that of stomach acid, it couldn’t even contain it itself, even if it produced excess mucus. Now, stomach grade acid could easily blind a person.
I’m not a chemist, not good with making code actually doing stuff, and not good at keeping things brief, so I would love to hear the opinions from someone who knows more about what they’re talking about.