She may be a grade pony, but she certainly has some good breeding in her background. I see some QH and something else in her; the something else added some refinement.
Many on this forum will disagree (with some cause, as she's grade and the foal would be unregisterable), but if she were mine, I would seriously consider breeding her. Her confo is hard to fault, and her attitude and performance are exemplary. I would take her to a fancy Welsh stallion and hope to get a spectacular show pony or a TB stallion for an all around sport horse in a minute.