the problem with a cavalry charge in game currently is
-Charge damage too low. typically a horseman will do about 10 damage to a looter when knocking them down. (in real life, just falling from a horse can result in paralysis or death)
-0 trample and collision for downed units. (people that get knocked down, instead of getting ran over by a horse and die, they have 0 collision and cannot be hit by a horse till they stand back up)
-0 collision for downed horses (in real life, there's momentum, just because a horse dies while charging, doesn't mean it stops, it's still a 500kg unit going towards your formation at 40km/h)
I'm not even talking about how a fully armored cataphract can take 85 damage from a peasant poop fork or how drunk these cavalrymen are when trying to hit people with their long sticks they miss 90% of the time. just charging physics, no need to make things crazy either. just slightly buff some of these numbers.
give a dead horse some charge distance before despawning it as a unit.
give more charge damage initially but make it diminish quicker (the second person you hit in the charge will have slightly more reduced damage)
give the chance for trampling. units downed will stay downed and take additional damage upon collision.