I think the answer is to change all unit types' hitboxes:
- Infantry: smallest hitbox = shoulder to shoulder.
- Foot archers: medium hitbox = armslength gap. 1-tile minimum range.
- Cavalry: large hitbox = double armslength gap. 1-tile range.
This makes intuitive sense: archers need space to knock, draw, loose and a horse is thick AF, while infantry can form tight units.
I imagine if all equally sized unit groups were in 'box formation'; the infantry would be able to walk right through the group of archers and the cavalry would not be able to do so, while cavalry's +1 range gives "first hit" advantage over infantry.
Infantry would be the least clunky and just need the proper formation and patrol into a fight, while archers would need some micro and smart postioning to be effective, while cavalry would require most micro to be most effective; tactics like pincer-moves, flanking etc.
This micro/skill requirement would make sense with infantry being considered peasants with sticks, archers needing much training and cavalry being highly trained, professional knights.
I actually really like this idea. Archers should be less effective against infantry at range (without thumbring). I don't think the answer is in the hitbox though, but rather you can just set archer accuracy against infantry to some lower percentage. That being said, I don't know what the current percentages are so I can't elaborate on how much they should be reduced.