As for transgenders, given the 80%, are you talking children who turned out preferring their birth gender? (If so, they're already not allowed surgery if not considering careful case by case, so that seems sensible)
Or are you considering adults? In this case they were people with a fully formed brain, who weren't in a direct relationship of power with someone more knowledgeable and experimented and thus are fully responsible for taking their decision alone. (this would be equivalent to a 13 yo regretting doing another 13 yo, not an adult)
The data I've found for regrets is 2.2% (767 persons followed over 50 years) (and another found out that Dutch trans men had a better quality of life than those born males, with more than 90% satisfaction ratios, from which regrets can be inferred).

I'm gifted and I can definitely tell you it's not a good idea, the two don't go hand in hand. We're also only 2% according to most estimations.
And then, as for developing earlier, the problem is: how do you qualify and quantify it? Establish it? Developing soon enough to do a 13yo and to have mature sex with an adult are paradigmatically different, as said above. That would require for super early maturity, which courts have estimated isn't frequent enough to be worth it, some even say it's not possible due to brain maturity. (note: when I said "children complained", I meant in general, a huge lot, I didn't mean it as "some")You could say it's illegal unless proven that the child is mature enough. But in practice, there are all the possible drifts that would go with a blurriness in definition. It would be hella concerning because with a pretty discourse it could harm children who are victims. Some could also be afraid of reporting it -even more so than they can currently be.

So behind problems that practice has put to light, these are the key ethical reasons, the pressure is far, far different and it can be argued that they don't know what they consent to because they haven't actually discovered it yet, only at best in an immature way.
If they discuss having sex specifically with that one person with family and doctors in a way that makes sure there is in fact no grooming, the issue is far lessened, as they have an educated adult opinion that can undermine a disbalanced relationship power.
But this looks like "lab conditions".

There are precedents: some hippie communities in the 70s also questioned this rule they saw as arbitrary, on these grounds. Law proposals had been made to change this, on the grounds that children were consenting and liked it. And then, children that had grown up talked and sought help because despite having consented at a time where they didn't fully understand (yet thought they did), they qualified this as a trauma, and it was judged that a symmetrical adult-child sexual relationship didn't exist. (you can look up Pierre Verdrager, The forbidden child, who explained the social mutations around pedophilia quite nicely)
Someone their own age, being equally immature, doesn't have the ascendance an adult has over them. They're both discovering, too. (they're also physically more compatible)

One of them relates to their own body, the second one to possible exploitation of this body for rape by someone else, hence the necessity of protection measures.
One of them also goes with discussions with the family and doctors, the other can be less thought-through and involve pressure -assuming we're not talking straight-up abuse with the adult lying.
But, the argument is sometimes made that some can be groomed into being trans too.
Well the legal age for surgery (which is mutilation only if your surgeon's bad) is 18, rarely under and if so, always with mandatory parental consent. Higher than for cosmetic surgery. Higher than the age of consent in some states. So except for a limited number of case-by-case patients, children who consent to having their genitals mutilated are in fact 18+ who can have sex.
Then, you can say that stopping puberty is technically an alteration, but by this logic "old enough to want to keep a child bod" doesn't go well with "old enough to have sex".

You should definitely open an Etsy shop, I'm pretty sure it'd sell.

En garde!
*charges, aiming at the top of your left arm*

Ok!
@snowbeast Sure, join the fight!
I don't know if we're going to play in teams, but in the meantime, *passes blade alongside Dr's saw to see how it sounds*
Sounds like possible death for everyone!

I really hope that it won't, but we're about to know.
Just for logistics, how long is your stick? (no innuendo)

Yes!!
This one https://musee-breton.finistere.fr/client/178/quimper04/1b80e930-fd59-41b2-8142-79beb732d8fd.jpg
What's your weapon?

Indeed, gals, guys and non-binary pals. Everyone in their right mind wants a private library and swordfights.

Me too! Or a sort of lollipop.

They've been informed! More and more people don't grow all four of them.

Why have I never done this?
I won't pass the opportunity a second time.
(I wanted to say "rawr" but I can't, not since the emos)