I gotta say, bariatric surgery sounds pretty bad after googleing it. Its no where near like trans surgery. Though, I personally think both should be banned for minors. I am of the mind that such life altering changes should only be made once someone is of a certian age to be fully responsible.
I do not have faith in teenagers or even young adults to know how to best handle their life when they are so young. Im in my thirties and i barely believe i make the best decision for my own life.
My concern are for the ones who will ultimately regret having made the decision to transition. There just should be a limit to any body modification for minors.