Your mare has many good conformational points. Her hind quarters are, IMO, her best feature. Good pelvic angle/length, strong coupling at the loins, Hind legs straigt from what I can see. Her front legs are also good, and shoulder decent. Her only fault that I see is her neck. It ties into the body on the low side, not connecting so wel with her wither and back on the top side. The lower neck muscle kind of bulges out. I think this can be remedied by riding him in such a way so that she lifts the base of her neck while extending the rest of the neck forward and downward, the so-called, "long and low".
You will want to encourage relaxation of that lower neck muscle and engagement of the muscles that cause the neck to arch , in the way that a horse arches his neck when excited or greeting a new horse in the herd.
Have you ever read any of the articles by Dr. Deb Bennet regarding how to correctly develop the horse's neck? She has a website, ( i would just google her name) and lot's of info on this.
Your mare looks really powerful. I bet she has a lot of engine under the hood.