I'll scrap the entire huge rant about the wide array of negative emotions reading through this whole thread has caused in me... it reminded me of the exact reasons I've come to find discussing Discovery completely unsatisfying ever since the pandemic started... it's as if positive discussion of this series doesn't even exist anymore, topics are always exclusively raised by people wanting to criticize something and anyone who actually likes the series is forced to stay on the defensive all the time. I just don't have the emotional strength for it right now with my own issues regarding my gender identity making it hard enough as it is.
So I'll just say that the whole idea of mixing up the trans allegory of choosing and customizing what you want your body to look like with the story of a canonically trans character who's at the same time also talking about his actual transitioning in the past... it was just so meta and folding in on itself in Ogre-like onion layers I couldn't help but chuckle, I loved it. The concept just feels so hopeful, as unrealistic as it seems from a 21st century viewpoint.
And that being said, yes, I would be ecstatic if this kind of medical technology existed. I've said it on this very forum twice: I would do unspeakable things for getting a customized synth body that matches my gender identity or some programmable-matter-powered remolding of my body into such a form. But. Big but. I refuse to even consider sacrificing the representation of 21st century trans performers in this series just because the extent to which our current medical technology allows us to transition simply doesn't match the imagined possibilities of 23rd-24th or 32nd century advancements.
By all means, if we were thinking "realistically", trans people in Star Trek's future could and should have access to medical procedures that could make them indistinguishable from cis people of their gender, up to and including fertility. But this would inevitably mean cis performers playing trans characters. Should we really sacrifice all the progress we made on achieving the – still meager – levels of LGBTQ representation we have in visual media today simply because having actual trans actors portray canonically trans characters in speculative fiction would ruin the viewer's "immersion" akin to a bad matte background and styrofoam rocks revealing that the planet Spock beamed down to is actually a soundstage? Simply because imaginary android bodies, bio-nanotech or magic fantasy shape-shifting potions could achieve far more than IRL medical technology?
And yes, I've said it before, others have said it before as well, don't forget that there is not one single unified trans narrative. Not everyone wants to transition in the same way or to the same extent, and there are many who wouldn't want to medically transition at all. But even then, restricting trans performers to playing characters who merely didn't have access to 32nd century "magic-complete-sex-change" tech, because the imagined end results of those would presuppose a performer outwardly indistinguishable from a cis person of that gender... how exactly would that be different from the actual transphobic diatribes leveled today against trans people not fitting societal expectations of femininity or masculinity? Portraying a utopian future for trans people through an explicitly transphobic BTS practice, now that would be true progress.