It is already happening men are competing with women in sports and people are convinced they can change their sex.
Mental illness is nothing new. Sexual dysphoria is not even something new. Many transgenders manage to grow out of it. They find their lives more miserable because they were allowed to mutilate themselves. From what I have read those who regret transitioning live with intense pain.
What this really is, is child abuse, plain & simple. The criminals are the adults that promote & support, and that is exactly who we should be going after. The sentence should be either death or give them the sex change procedure they so willing provide to others. But let's limit the penalties to those that do it to underaged children, including providing puberty blockers.