Great vid, watched the whole thing.
You've got a more complex commanding strategy than I have. I keep it much more simple where when I'm fielding large armies I have my infantry largely following me with my archers right in front of, then move them behind when we are about to clash. I use my cavalry to attack the enemy right before the clash mostly to cause chaos in the enemy.
The big challenge is making it so your forces are all engaged at the same time effectively which is what cost you the fight, you clashed with the enemy while the majority of your infantry were playing grabass down the river for some reason