I don't have a picture of her pulling the drag but here is one of our mares pulling part of a sled. She is a Bashkir Curly, which generally have solid bone structure and have a bit of a 'drafty' build to them, but she is a touch over 15 hands. Once they accept pulling the weight and the noise (as well as seeing something behind them), which isn't much, you can just lead them around and pull the drag. Any horse with a sane mind is plenty cut out to pull a small drag. Seeing as our four-wheeler is kaput it is easier convincing her that pulling is what she was meant to do than coaxing the four-wheeler into running.
I support the idea of horses working for their keep, but this diet plan doesn't work when certain people, who will remain nameless, give them treats like they are going out of style.
But I don't think you need a draft to drag an arena, even a pony would do. A pony certainly would eat less. ;3