I am not asking this to be transphobic or anything but I had this debate with myself at 2 o’clock in the morning and every time I remember it I can’t focus.
On one hand, it is what they want. Let’s assume it causes no harm to them or any unforeseen circumstances.
On another hand, it would erase their identity as trans people. At the extreme you could consider it a genocide, since turning them into what they want would mean there is no more trans people and their unique identity is erased.
They’re already the gender they are. So your concerns about erasing their identity are warranted.
I think you might be conflating sex with gender here, though. Gender isn’t based on anything objective, it’s a purely social phenomenon. And while most of us identify as the gender typical for our sex, some do not; that’s what it means to be trans.
Some trans people want to alter their primary or secondary sexual characteristics to better align their presentation with their gender. Those people might take you up on your Thanos snap sex swap deal if you offered it on an individual level. But not every trans person wants to change their body, or not so drastically, or not all at once.
And as others have said, magically altering someone else’s body without consent is fully evil.
Yes, my native language does not have a distinction that is as obvious. I meant that their sex changes into the gender they identify with in my hypothetical scenario.