Add fatigue and maybe alter the frequency of cavalry breaking through the front lines (since we can't flank which is how real cavalry dealt with archers).
Infantry and mixed fatigue at a rate related to armour quality and training, ranged fatigue at a rate related to range and training, cavalry experience minimal fatigue (which was part of the point of riding horses), special forces align with their respective unit type, but fatigue less.
A big issue is infantry in box to stall the enemy while R5 ranged keep firing. By round 10 when the enemy approach the ranged units, they should be fatigued and not dealing incredible damage.
