If the procedures got so good that a trans woman/man was indistinguishable from one born that way who would still object to them claiming the gender they choose, most of the arguments fall apart at that point.

Almost everyone who opposes trans people's existence today. Opposition to trans rights is rooted in patriarchal hegemony and the control of bodies. Our existence is a fundamental threat to the foundational perspective of the predominant power-structure in society.

No one does a womb-check before granting women validity. It's always been a vibe thing and people who do not conform to the prescribed model of existence as a man or woman are constantly denied full privileges under the framework. It's not just trans women getting the short end of the stick here, it's everyone: men who do not embrace dominance culture or otherwise display "effeminacy" are denied true Man status, women who don't meet beauty standards or possess a submissive demeanor are slurred as bull-dykes or the dreaded transexual.

This isn't an issue with any real reasonable basis for it's opposition, it's a golem of pure hatred and disgust in a suit vs. people who want to live full, free lives.

editing to add: the first known uterine transplant was performed on Lili Elbe who received treatments through the Institute of Sexology in Germany. The Institute was famously destroyed by the Nazi regime. It's barely coincidental that fascism has risen again as medical science brings this technology to maturity. Trans women gave their lives for this medical miracle.

They would just move to calling the procedure a violation of the "natural order" - "Lovecraftian horror", "Frankenstein arrangement", "something Mengele would do" - argue that it is akin to rape, create conspiracy theories about uteri being stolen, and/or invoke "Think of the children!"

I saw all of that already. Some of it in this very thread, some of it on the defunct /r/GenderCritical: I remember someone proposing committing suicide by volcano to keep her uterus out of "male [sic] hands".