Warband recruitment is a very thematic system, but in play it often feels weirdly limited, so I propose a minor update to it that also makes it more consistent.
This suggestion is focused most of all towards dark fortresses, but could be applied everywhere, but would probably want different specific values.
Firstly, increase the capacity of each unit in warband recruitment. A max of 4 for marauders (this may be without a building) is simply tiny, and with many units not getting above 1 or 2, recruiting armies is very slow, and it's often not worth returning to your fortresses. This would also let it tie into the main change better;
Secondly, and more importantly, change how units are added to the pool from random chance to filling a percentage of the cap every turn. So having a capacity of 10 marauders and 5% fill rate would mean every turn you get 0.5 marauders, or in practice get a marauder every 2 turns. This would let it be reliable to fill up the selection, and it could still scale with all the current factors it does, as they make sense. It would also make a well built up and positing dark fortress provide a reliable stream of a given group of units, be they specifically marked or mountain units.
And... that's about it. Otherwise the system, even if not my favourite most of time, is interesting and thematic, but it makes it very awkward to make an army as chaos that isn't random stuff thrown together. I would also want a higher cap for how many gifted units can be stored, it is currently very low, but the per army cap is alright, if it could be a bit higher.