This is going to be very controversial, hopefully I get some support, please be constructive in replies.
Realistically, a lance is a single-use weapon. They are typically very heavy and the force of collision, combined with an impaled target, is likely to cause it to shatter, if not fall from the lancer's hands. I'd like to see this feature inserted into cRPG in some way without nerfing cavalry or discouraging the use of couched lances. Here is how it would be done:
1st: the damage of standard lance thrusts would be reduced and rely entirely on speed bonus (I know I'll get flak for this, but in history cavalry tend to rely on their mount's speed for damage rather than their right arm)
2nd: the damage of couched lances would be increased
3rd: a couched lance entering a player's hitbox will cause them to be knocked down
4th, and the most important: lances break depending on a factor resolved from the lancer's polearm weapon proficiency and the lancee's armor
5th: if a lance does not break when it contacts an enemy, the couch will NOT end and the lance can continue to damage more enemies
So, you couch a peasant wearing naught but a tunic and your lance is perfectly fine. However, if you lance the guy in the gothic plate, your lance will break - unless you have (X) polearm wpf.
You spot a pack of six peasants, and if they're standing in a horizontal row, you can lance all 6 of them. But if there is a tin can in the middle of that peasant row, your lance will break on him, and you will only kill three peasants.
Edit: some clarification after I reread. Your lance will still damage an opponent if it breaks (perhaps at a reduced amount?).
Thanks for reading, please tell me what you think! You can't tell me it won't be fucking awesome when you mow down a couple of players, your lance breaks and you're forced to draw your sword to fight your way out!