I like the idea to make mounts something special. Also i like the idea that you have to feed your Mount and take care. Maybe it would be cool to get a little level-up system for mounts, that offers some small benefits. For example: at level one you can faster mount, dismount, on level 5 your Mount is able to wear some kind of Armour or saddles and on level ten you can equip it with some kind of prestige- Armor.
Also, it would be maybe a good idea to get some kind of barn in the housing system. Some system, where players can "hire" an NPC to feed and take care for their mount. That could maybe be a good idea for casual players, that doesent play that often. Also it would be a system where players had to spend some money, so it help to prevent inflation ingame (what is a great problem in many MMORPGs). To prevent, that players just put their Mounts in a barn and never touch it again there could be maybe a Mood-system for Mounts. If you ignore your mount too long it gets sad and slowly loses levels?