This is an off-the-cuff suggestion, but it struck me as a simple enough idea.
Promoting soldiers one by one might be a good way to custom-tailor an army with the fittest, bravest, most expendable force possible, but to form a sizable force it strikes me as something that could get tedious… as it can in certain other games, cough cough. So what if we had a “Volunteer” setting for the army?
With this mode active, certain villagers would sign themselves up for military service, independent of any micromanaging on your part. There could be a lot of under-the-hood factors here; personality traits like aggression, bravery, mortal grudges against goblins, peer pressure from friends/family, and so forth would persuade villagers to volunteer.
A soft cap for the number of volunteers could be set either manually or by the “danger level” of the town, dependent on how often and how badly the town’s been attacked; a safe settlement without a care in the world might have a handful of paranoid or boisterous sorts who sign up for fun, while a fortress under siege would see its people divided between those too cowardly to fight and those too brash not to.
If nothing else, an option like this would allow for a bit of set-and-forget to handle early town defense, and perhaps keep recruits flowing in if/when things get too big to manage. What do y’all think? Good idea, bad idea?