Civilians in an outpost really are more like refugees than settlers.
They are incredibly ineffective at working in an outpost because they won't get the bonus production that vassals get, so all you can really do with a civilian in an outpost is have them work an agricultural plot to cover their own rations for existing. They could probably also work the IDEK plot, because early on, you're likely to be using workers who don't have a need for the equipment resource, and a worker on an agricultural plot would be better for you than the civilian, while you're going to have a surplus of equipment anyway from the IDEK plot. If you do *anything* else with them early on, they're costing you 10 rations that you're probably always short on already, and not really putting anything back into W/R/E/C, essentially wrecking your early resource management. Now, if your game has progressed to the point where you might be able to afford the spare rations for civs that don't put anything back into W/R/E/C, you could have them doing something like tending your tatos, mutfruit, and corn that you use for your personal adhesive production, but even that is assuming that you don't just use naked protectrons for your personal farming needs.
Now imagine having a dozen civilians in an outpost that you just liberated, and you can't send them *anywhere* else but another outpost that doesn't need or want them. With a heavily skewed ratio of soldiers to civilians, the outpost's morale tends to crash pretty hard. The Conqueror system doesn't have this problem with civilians in outposts, because you either kill them or enslave them and ship them off to work somewhere else. The Liberator system, on the other hand, truly does need some sort of "refugee" system to take the place of the slave system, to allow liberators the opportunity to do, well, *anything* with civilians other than simply execute them. Maybe we could add some special plots that allow civilians to work in outposts and actually be productive without the vassal production bonus? Is it even possible to make plots that can only be built in outposts, and *not* in vassals or settlements? Maybe we could even use the same system as conquerors, only instead of "capturing slaves" we "liberate refugees" which we can then send to other settlements. If we cannot find a viable way to send civilians from an outpost to a vassal or regular settlement, we really do need to find some way to put them to use at the outposts in which they are forced to live like refugees.
One other point I thought I'd make here, is that I recall some faction packs having faction civilians in them. I think the Brotherhood of Steel faction pack was one of these, where civilians that showed up were scribes and engineers. I also recall the Children of Atom faction pack having faction civilians, which were essentially brainwashed cultists that were not warriors. In cases like these, the "fluff/lore" lines between civilian and soldier are much less defined, and it is pretty logical for military outposts to have some civilian personnel. Would it be possible, or rather, practical, to create some sort of system that allows for these civilians to work and live in outposts while retaining their civilian status? The system that liberators have available now has such a high opportunity cost that it is not viable to have civilians in an outpost early on, as this is when W/R/E/C is most fragile, and the problem with rations in particular will greatly hinder your ability to recruit more soldiers and expand your influence in the very beginning. So far, the refugee problem has been the biggest I've had as a liberator, and the most viable solutions I've found were to either: a) use the console or some other mod to manipulate the settlers in question, b) execute all of the civilians in question (which I was unwilling to do), or c) simply withdraw my control from the outpost and let nature take it's course (either letting the outpost be taken by another faction, or letting the settlement decide to just leave on it's own).