I'd love to be able to earn bonuses for flying/driving/commandeering mounts for extended periods of time, maybe even encouraging the use of different mounts (like there could be flying mounts, driving mounts - each type of mount you could earn a different bonus for, after so many hours of flying/driving it [hours in game]). It would also make use of the temporary mounts that we get, that maybe those of us with permanent mounts never use - different types of mounts could bring different bonuses, maybe in game items or coins, potions, that sort of thing.
Not sure how feasible this is, but it's something I thought I'd mention and suggest?