I have something that could be very useful for this in my campaign (and supplement I've been working on largely based on it)!
Trust Skills
I designed it with dealing with outside factions in mind, but it would work equally well for a small group of reluctant NPC followers, with the idea that yeah -- everyone in this world is a survivor and not likely to take dumb risks to change that.
Works like this: each faction, sub-faction, or group is treated essentially as a "skill." They have trust in you of rankings A, B, C, D, and none. When you want something from that group (that they are reasonably able to provide), you roll your trust die. The ref should apply modifiers as appropriate (is the ask of a suitable scale to the PC's reputation, is it something that furthers the goals of the group, how valuable and useful is the thing they want otherwise, etc.)
- If you get multiple successes, they will go out of their way to grant it to you at low or no cost. (they prioritize your mission)
- If you get one success, they will provide the thing you want, or some equivalent, at a very fair cost/expectation in return. (they give your mission good priority)
- If you fail, they will provide what you want only if you meet some significant other demand. (your mission is of lower priority than whatever they already are dealing with)
- If you get a mishap, you have asked too much or too poorly and you must either make rapid amends (probably by fulfilling a significant ask) or lose a rank of trust with this group.
You can push this roll, but a mishap while pushing the results should be even WORSE. Using the results of another roll (such as persuade or command) or simply the basic roleplayed approach to determine the modifier is usually a good way to go. I try to always communicate to the players the general scope of how the other group might interpret this before they roll.
It may sound like there's some overlap with the bartering system but you absolutely
shouldn't use it for basic requests of material goods. You should use it for big, mission critical things, personnel, or NPC tasks.
"We are going to locate the Baron's HQ, but to do so, we'll need to requisition one of the few operating armored vehicles, and fuel to travel 100km and back within 3 days."
"We located the HQ and have good intel on the terrain and defenses. We need 10 good fighting men to support our raid."
"We are setting out on a recce into enemy territory. While we are gone we need a small team to go deliver an important message and this wagon of goods to the local magistrate."
"We want to take the only healthy adult male away from your family farm to scout the heavily mined fields up in front of us while we trade pornographic magazines and observe from very far away."
Context and position obviously matter a great deal. This makes it a super easy flexible way to deal with such things that also brings the goals and ambitions of groups of NPCs into play. It works better for dealing with outside parties than with direct reports and so on; there are already rules for that more or less. But I'm gonna do a little thinking on how I might adapt this system to better fit a small group of NPCs that are "permanently" interwoven with the PCs.