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.
That’s why it has to be a choice.
Society at large is a community identity too, and many trans folk value that community connection more than I do for example. Many of us would absolutely choose the magical option you suggest in your initial post, but for others of us like myself, it would come with an incredible sense of grief and loss. I spent my life learning to embrace and love this part of who I am, and to have that taken away, just so I can blend in to the society that made the process so hard in the first place, that would be a punch in the stomach for me…