make rouncey/palfrey/steppe/desert 6riding, destriers/coursers/arabians 7 riding, armoured horses 8riding.
add in "weight limits" for each horse so for example if you are riding a courser the total weight of your equipment can't exceed say.. 20? (this is just a random number but you get the idea)
make melee weapons do the same amount of damage to the whole horse as they currently do to the legs and nerf ranged damage to horses by atleast 1/2.
ez.
Some interesting ideas, if they were to increase riding which isnt a bad idea i think it should be 1 up from the current levels to help maintain balance between horses. Some horses have higher riding to compensate for them being better than other horses (courser/arabian). The weight limit is interesting aswell, although the vast majority of cavalry do not wear heavy armor, its mostly light or medium. Also heavy horses really need to be made viable again the leg nerf is really killing them.
What REALLY needs to be done here is to make cavalry more challenging than it is. And im referring to lancer cav mainly. The problem is that its too easy to hit someone with a lance on horseback. Hitting someone should be made much more difficult. Its just not hard to stick your lance out and ride straight into someone, couching is difficult as it incorporates more complex mechanics to pull off, but just stabbing someone is easy.
So how do we make that harder. You could make couching easier and make it so that lancer cav always had to couch. Make it similar to couching but changes in terrain dont cancel the couch as alot of maps are very uneven and maybe even reduce couching refresh time and nerf couch damage a little (and lancers usually "couched" in medival times so why not in crpg, the lances are long and heavy enough that it would be hard to use them on horseback the way they are used in crpg). When your couching its harder to control the spear, you cant quickly turn it in another direction and it just doesnt have the control of a regular lance thrust, this is the kind of thing we need to go for.