I would like to have a spell that toggles "Horse appear" "Horse disappear". Then I don't have to worry about him getting in the way if something attacks or looking around for him when I exit a dungeon.
Abracadabra 1 - "Sweet! A horse. Just what I need."
Abracadabra 2 - "I don't need you anymore...bye!"
This + disabled fast travel = transportation bliss.