Reduce cav maneuver, but buff hitpoints and armour rating, maybe speed too.
Less maneuver means less unpredictable. Which makes the player with suckish awareness more able to predict the direction of nearby enemy cav. Cav will need to plan ahead, cause they can't get out of hairy situations as easily anymore. Still they get a little more room for mistake with more hitpoints, also making up for being less able to dodge ranged fire.
Also, how bout them deployable stakes? I don't mind if they can't actually damage cav, stopping is enough. Could provide a nice tactical element and some safeguarding for archers if they can't roofcamp anymore.