First my thought. NPCs spawn in groups, even if it’s 1 member. This concept works similar to how Mount & Blade functions. The group does everything as one, yet individual activities are given if they are needed, and the characters Spawned in. A faction is created when a group establishes a settlement, a home base of sorts. Thus groups within the factions can easily gather when needed. Groups and factions have different ways of being lead, depending on it’s leadership style and rules. As the game goes on, groups and factions become rarer, but bigger and/or stronger.
This goes into the next part. Under most leadership styles, you don’t control other people. You can of course provide a uniform or make a uniform. You can offer them the clothing and weapons for what they do, but it’s their choice to take it.(Provide) or you can make a uniform, and of course the NPC can either take the uniform, or say “F*ck this, I’m out!”, or something along those lines.
Also fighting styles. A telling an explosive happy man not to use explosives, he’ll laugh you off. A quiet style won’t go loud, and a loud won’t go quiet. You can force, and they can leave, or you can provide, and they can say no.
Now, there are cults and people who give their entire being to you. Those, you have a ton more control over, but are hard to make/attain.
You can always buy something they don’t exactly need, you can also ask to borrow. Takes some trust, which you can regain by returning it.And training, if they like you it’s free.
Also, for the most part they won’t just follow you. Most want to know beforehand where their going, and why. “Hey, want to scavenge at this house?” “Sure, take the lead.”
Gaining trust. help with tasks they do, bring them better stuff, fix them up (requires trust in itself),training them,teaching facts, and simply asking before doing. “May I come into the settlement?” “Well, you did help build the outer wall, why not.” Where otherwise walking in meant being shot, or what not.
Also the closer you get with another, the more it hurts to lose them, but friends can help ease some pains.
Any other thoughts?