i second this idea. i used to HAVE a horse... and sometimes, just for fun... i'd wander around the field with her with nothing more than a halter, and a single lead rope...

animal lore would probably be the easiest skill to base it off of... altho realistically, it would to some degree be more training for the horse, not the rider. the only reason i was really able to pull that off... my horse knew western-style neck reining. i wanted her to go one way, i pulled... i wanted her to go the other way... i layed the rope agaist her neck. if she didn't know neck reining i'da been sunk.

just my 2 cents