You cannot retrofit cultist minor faction recruits. Is there any means by which they become stronger over time? Or will late-game recruits be just as weak as the very first recruits I might get in the first 20 turns?

They're kitted out the same as mercenaries, with the iron/dust gear for the relevant tier. I am 99% sure they stay with what they get when they spawn, though, but all the new ones you get will be stronger.



In the files they have a different design list than the mercenaries, which means that they might have different weapons equipped, but I've not checked that.

Yes, they´re much weaker than equipped unit, even though they do get stronger through levels. You want to use them as an utility tool - if you can get fast/flying units, use a couple for scout/vision; if you can get tanks/damage dealers like haunts, daemons and minotaurs, you can use a 6 unit stack either as cannon fodder for your main army (units that will indeeed die fast but at least will soak damage and provide morale) or as a distraction sieging unimportant cities to draw attention.



You definetely don´t want to count on them to be your standing/conquering military. Instead, after you´ve depleted their utility, just sell everything to reduce upkeep and make money for strategics which might be hard to extract.

They can also be turned into privateers, to attack empires you currently don't want to be at war with.