Having my partner masturbate in front of me is guaranteed to get me going - but I'm not sure if the words will achieve the desired result.
Thing is, your wife's issues come from inside her, and so the solution must also come from her. You could say all the most wonderful things in the world, but if she doesn't believe it, nothing would change.
What's she doing about fixing her body image issues? Counselling? Diet and exercise?
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.