This could rear itself in a lot of ways. Imagine that cavalry dismount their horses to ford a river, speed up to close the distance between enemies, or slow down while the army is traveling.
It’d also be cool to see units from the same "family" interact with one another. Maybe WW2 soldiers will try to save or patch up their fellow injured soldiers. Or a group of roman centurions could form a phalanx.
This would help lend more to life to each character type and family. Currently, all units use the same AI processes causing them to feel like bland numbers. It's just not very interesting.