Adding Horde Options

I would like to make some specific options possible for the dynamic spawns of hordes. I have done this in previous builds (I think when they first came out) but they didn’t quite work as I intended. Wondering how exactly I could achieve these effects:

1.) Hordes can grow slightly over time (could be dependent on the type of monster, maybe triffids breed, which could be in already, and zombies don’t, but specifically I DO want zombies to replicate. I know it’s not realistic, it’s what I want. Maybe simulates more zombies or other corpses re-animating? Value could be a number, 0-100, as a percent increase per 24 hours to save on overhead. This could be expanded (outside of what I want) for maybe some robots to build more of themselves using spare parts around town, or other things I can’t figure out.

2.) Hordes cannot be permanently destroyed OR, failing that, new hordes can spontaneously generate. I want there to be an option for the game where it’s EXTREMELY difficult to be safe anywhere. Walking outside, zombies are almost a weather phenomenon, and the hordes might be like clouds. With the spawn density set high, perhaps no city would ever be safe. That is the goal.

There are other things that might be neat (like the % of different types of monsters in a horde) but those are what I’d like to modify my game.

The way I originally did it was to not subtract monsters when a horde went under 50, and I simulated growth by adding a percent check when a monster was added back into the pool for a 2nd one to be added. This gives motivation to NOT avoid zombies, if you want to clear a town.

Again, not saying it is realistic or fair, just options. So there could be many small hordes, a few big hordes, a lot of big hordes, and they could regenerate or not. Where would I optimally start or add these changes? I feel like there was some cascading effects to these changes I couldn’t track down, and there was another function that changed monsters I couldn’t find.

[edit]

So been poking around int he new files, and I can’t find exactly where the spawn population is kept anymore. Does overmap::add_mon_group create a group, or re-add an existing group? There used to be code that subtracted population units from a spawn area, but it looks like maybe some of this is stored in .json files. Basically, I’m looking to create a boundless supply of zombies in every area, but not have them all spawn at once. Is there a way to do that in the JSON files?