System where mounts gain levels too, maybe by taking some % of exp from riders
share
Would propably make riding guilds more popular, mounts more valuable and
keeping them alive worth something.
Would make longterm riding / use of same mount add some extra flavour

And no, im not saying this because I am a cavalier (don't really use mounts)
and saying they need an uptune, but system would propably courage me to try
them at least, feel free to flame me, its just a wanted idea, and afterall
this is just a game with own little perverted social life.