I don't think that preset factions would fit well in the game.
Rather than have these different factions form on their own in the exact same place every time, let the players influence just how territory changes hands and what factions form. Have the game start with no factions as the quarantine was just recently placed on the game area, and have NPCs/the player form them on their own over time.
Allows the player to feel their actions have direct consequence earlier on. Clearing an infested warehouse and coming back later to find bandits have set up shop is a more enriching experience than the warehouse having always had a preset group.
Deeper player agency as they discover what actions can be taken to ensure different consequences. For example, this could be helping someone badly hurt, and weeks later when they're the leader of a nearby group they might be more receptive to bartering.
Instead of the prison always having a tough set of armed inmates, let the game decide what outcome happens. Say the prison always starts with a dozen inmates, and five guards. What are their traits? Upon world generation, the prisoners could all end up psychopathic, athletic brawlers that massacre the guards, or a mishmashed group of craven gardeners and hunters that are quickly put in check. This means several things:
The results add variety and depth to the prison area
The player could arrive at the prison early and directly influence the outcome
This allows for deeper consequences. You could help the prisoners take over, and then later they could ally with your own faction, or perhaps they just decide to terrorize the entire Rosewood area instead.
I think there's just too much to be explored with more RNG-decided factors, rather than preset factions.