At the moment, units are arbitrarily divided into sword and spear melee categories. I would argue that this distinction is bad for the following reasons:
Few soldiers equipped exclusively swords, which were primarily a side arm.
The representation of sword units being a counter to spear units is ludicrous for our purposes during the ancient times. Instead, disciplined all infantry formations should always be able to withstand frontal cavalry assaults. Any differentiation between spear and sword wielding is similarly arbitrary.
The spearman, a unit type that is countered by sword and ranged units, is largely ineffective against cavalry due to a lack of adequate mobility.
Thus, there should instead just be melee infantry and melee cavalry, with subtypes based more around armour and training yet still retaining the core functions of their parent categories. This would greatly streamline one of the game's more unintuitive aspects.
I've intentionally kept this brief and would be willing to elaborate my points if needed.