In my eyes the ideal halter horse and the ideal driving horse would look slightly different. The driving horse would be heavier boned and possibly slightly cowhocked. The halter horse would be very refined. Idealy they would both have perfectly straight teeth great movement, beautiful heads, and upright necks. The driving horse could have a slightly longer back than what I would like in a halter horse. While breeding for the perfect halter horse you are bound to get some that are more suited for driving. I don't know if there is a need to breed specifically for that. Maybe as the halter horse becomes more and more refined a person might want to add a bigger boned mare to the herd. From what I have seen there certainly seems to be no need for it at this time.