Tamren
I suppose given that the unit creation system is a lot like lego
That's what i would have to presume, given the info we've been given so far. You seem to presume that army creation is similar to HoMM (ie can consist of as few or as many as you can produce). However, I was thinking that troop production would be more along the lines of Total War (ie each group consists of a set amount of soldiers). I'd like to know which it is because I was thinking of how you would include officers in the army system. With the HoMM method, i'm not sure how you would go about it (maybe placing a more experienced soldier with better arms in but i still don't see how that would work). With the TW method, you can simply pay/train/level-up the group and they get an officer with slight group buffs.
The officer and the group can then also gain further experience. The computer can auto-generate names for your officers, who go up in rank (according to exp). Place a soft cap on officers. The soft cap adjusts to how many officers are in each rank (eg low soft cap for sergeants, but once you reach xxxx amount of sergeants, the soft cap increaces. same for other ranks) Once an officer reaches a certain level, you can choose whether he becomes a hero, a general or elite officer.
Once you decide the route your exp officer takes, he also takes with him his specialities. So, for example, you have a swordsman who has fought predominantly orcs in a frozen climate. So he gets the orcbane trait, along with increased movement/survival in colder climates and receives an attack bonus when using a sword. Heroes and elite officers are self-explanatory. Generals operate similar to officers but instead of commanding single groups, a general can be placed over x-amount of groups (with prescripted commands).
I wouldn't want this officer advancement option to replace the wandering heroes who call to your fortress. They're the badasses who can be imbued with essence.