I would pass if I was shopping for one, Id ride him if I already had him, Nice withers, and back. Looks ok in the legs but not great. What is the diameter of his cannon bones ? What size renegades does he wear ? Whats he look like from the front, IE heart girth measurement, What is his resting heart rate ? He has a power rear as opposed to an endurance rear. May be better in barrel or sprint type stuff. Id want a flatter croup higher tail set, larger feet and thicker cannon bones if I was shopping for an endurance mount.
Your asking specifically about confirmation, lots of other things go into making a good endurance ride though. Best shape horse in the world wont do you any good if he is a nervous nelly and spikes a heartrate at the vet check due to nerves. Or wont eat drink on the trail. But from a picture or first look all you can go off of is looks.