Warband does horse riding great, because it isn't some horrible attempt at "immersion" or "realism" like Red Dead Redemption (wasn't good controls but great game) or Zelda or Shadow of the Colossus. These are all good games but slow paced single player adventure games with quite awkward horse controls, especially in steering and acceleration. I don't know how many other titles have attempted to emulate horse riding or if any had a good approach to it, but people should post them if they have examples.
Warband's style is pretty much ideal for a multiplayer, competitive, fast paced (and FUN) game. WASD, and simple. W accelerates, D deaccelerates, high speed means low maneuver and vice versa. Adding more to this will just make the player achieving what he wants his cavalry character to do in game more cumbersome, and ultimately less fun to play.
If you want to limit the round-long power of a cavalry character then punish them for going at max speed at all times but not too greatly with ya know, the recharging stamina bar. Anything more than a "very slight" limitation on horse mobility in this way would probably be pretty shitty to play, so I'd recommend not doing it at all.
If you think you have a point to prove with the horses just being motorcycles in game, then for the love of god please with a patch sometime soon replace all horse models with motorcycles and let us decide for ourselves.
