It's true it does look like a neat idea but as it has been posted, it's not very versatile is it. You would only be abkle to do the main part of the body. Also one of the reasons you give a bath is because of that water pressure a hose provides so what happens when all it does is trickle down on top of the horse's coat?
"without removing oils from your horse's coat"? HUH? Do you really wash your horse THAT much to cause his skin to dry out? I live in a province that is considered to be dryer than the Sahara Desert and my horse's "oils" are fine after he gets a bath. Sounds a little silly to me.