Okay, this one is pretty simple. This system works like a charm in Mount and Blade: Warband for example. Basically the player can make categories for the units. It would be very helpful to have a feature like this in EWoM as well. Ok let's see....
Example: The player designs 5 different units. a.) Longbowman, b.) X-bowman, c.) Slinger, d.) Swordsman, e.) Axeman
After that point, the player makes 2 categories: Ranged units ; Melee units -> Unit a, b and c = Ranged units ; Swordsman & Axeman = Melee units. Unit categories should have a new in-game screen of course.
This was just a simplistic example of course, you can make whatever categories you want. Summoned and tamed beasts, the various mercenaries etc. should be available for categorization as well.
Why do we need this?
1. In tactical battles the player could make all of the units active with 1 click in a given specific category & give orders to all of the units in the same time, if it's needed. This would be extremely helpful in epic, large battles.
2. It would be easier to keep track on the designed units. Example: What if you don't want to delete your old designs? Even weak, obsolete units can be useful in masses. So simply create a new category like Melee.Obsolete.LeatherArmor and you put all of the corresponding units to that category.
3. I've made a suggestion about a separate & informative Army management screen a while ago. Hopefully we will end up having a screen like this. If it's ever gonna happen, it would be good to see categorized units.