Horses would be fairly simple. Give them mechanics similar to a cow but with the saddle they can be ridden like a pig and controlled by the user via the saddle. The horse would have a fast speed once the player has mounted it. This would make traveling across large distances easier. To tame wild horses a new "rope" item, or just using string, create a lasso. Then capture the horse with a certain %chance (maybe like how fishing works.) This idea would be helpful for moving around large areas and the mechanics of the horse would be easy to modify from pre-existing mobs.