So, I've read a couple threads on this topic, played against cav ingame and played as cav ingame...and I have to say....I think I've figured out what would really balance this class.
Reduce the Acceleration of the horses.
Currently, horses can go from 0 to top speed in literally no time flat, despite the fact that they may or may not be covered in plates of steel. I mean, cavalry players in crpg literally have nothing to fear from anyone who isn't hold a pike. Why? Because, they know that even IF an infantry players sees a cavalry player coming and readies his pole arm to stab, they will most likely trample them if they miss the lance. Cav, shouldn't just get off with with a small smack on the wrist and a possible kill.
Decreasing the acceleration of horses would require lancers to think more tactically about their targets. At present, Cav players don't need to build much momentum to even ready their lances for an unblockable, instakill couch. This ability can be used for an unlimited amount of times durring the course of a game. A couched lance isn't something that can be pulled off as easily as it is.
This suggestion honestly shouldn't affect anyone who doesn't solely rely on couched lances and tramples to play cav effectively, while punishing people who play the class poorly.