Bukkit

I'd love to have the option that i can summon a horse with a spell (for example a book) where i can right click with to spawn a tamed horse, equals a random horse, but tamed. Another cool option would be if the inventory of this spawned horse would be saved, so it's not a random tamed horse anymore it's now officaly everytime you use the spell your horse.

So it's basicly the same as you did above with commands, with a book where you can right click with :) Maybe another rightclick with your book on the horse "desummons" it, and when a player disconnects the horse gets saved and "moves out of the world" or disconnects too (I know the disconencting part sounds terribly stupid :P )

You could add an option in your config to enable/disable spells, and when enabled you can choose an item (set an id) and that item will perform the summon command (/horses summon [name]) and select a random name, just for database storage reasons. the name doesn't realy matter. Or it sets it automaticly to maybe [yourplayername]'s Horse. If you have 2 books (equals 2 horses) the second horse will be named [playername]'s 2nd Horse.

Just an idea, but i think from what you got so far this would be a fairly easy step :)