Am not sure how well those changes would work, for the following reason: if you fight against a high initiative summoner, your precious cavalry will be surrounded by skeletons negating their movement and charge dmg bonus, while you pelt them with arrows / spells.
This is a problem with how summoners work. I personally don't understand why a summoner can summon their dude anywhere at all on the map. I mean, I get that archers have unlimited range, so you might ask why summoners shouldn't, but I don't think archers SHOULD have an unlimited range either, so there you go. All of that aside, if you get hemmed in by enemy units, tough. You don't get a charge bonus, as you shouldn't if your cavalry are surrounded and unable to move.
Also there is no tactical phase (like in heroes series for example) where you choose how your troops will be deployed on battlefield, it's pretty random, and depending on maps you can have cavalry blocked by other units.
This is true. This is still a problem with tactical combat that has not yet been resolved. It needs some kind of solution, I agree, so at the moment it would be kind of lame, but on the other hand, your horsemen would get to move the next turn so the momentum bonus would still apply on that turn instead.
Not to mention how movement is restricted by enemy units, a single tough unit is enough in a good position, to prevent all mounted troops to reach the back row units due to 1 square movement near enemy unit restrain.
Yes, and? If they position their defenders in such a way you can't run past them, that just means you're forced to kill the defender before you continue moving. I don't get the issue, it makes sense.
And finally, I believe developers intent with horses & wargs is to give a technological advantage (movement, defense, initiative, immunity to prone etc) to units using them. AKA mounted units are superior to pedestrian ones. You can only mount sovereign, champions and your faction units. You won't see a troll, ogre, dragon mounted And with this am perfectly fine, they should provide advantages.
Technological advantage? They might give you a "technological advantage" if they weren't the second technology along the warfare tree. You can grab horse technology way too early for them to be as overpowered as they are for purely "technological" reasons. And besides, cavalry units are and were never strictly superior to infantry units. Both had their uses and downsides in terms of upkeep, deployment, and maneuverability, both in combat and out.
Also, as many people have pointed out, immunity to prone makes no sense. People on horses could be knocked from their saddle in battle, and often were.