As for Raene, maybe this is just me misunderstanding (because I admittedly don’t understand the trans perspective very well), but wouldn’t she want to get gender reassignment surgery? Isn’t the whole issue behind being trans that she wishes she had been born into a body of the opposite sex? If so, surely she must want to take steps to “correct” this, given the option. If it were possible for trans people to just learn to accept their bodies as they are (as seems to be the direction this game is going with Raene), then “being trans” wouldn’t really mean anything, would it?
You aren't wrong with this point, the only issue is that this game is definitely not taking the 100% realistic approach with this kind of thing, not to mention there are more than a few trans people IRL whom have the resources for the surgery but choose not to get it. I will admit I don't understand the trans perspective too much myself, but from my understanding for some it isn't really about becoming the opposite sex, as it is just being in a body that doesn't make them feel uncomfortable when looking in the mirror.
IMO it wouldn't take much for Ziv to transition alongside Raene for morale support. I think the dynamic of a fully female member of her race would actually be more interesting than just another homogeneous member of her society.
Surely they'd have the technology in this sci-fi setting to make it 100% realistic and functional too ...
They most likely do have the surgery to make it functional and realistic, the issue stems from this being an innate part of Ziv that she hasn't given any indication that she would be willing to remove it. As far she is concerned, she already is not just another homogenous member of her race, her race of aliens is very bureaucratic in terms of love/mating, and she is definitely not like that.
Also, I think it is important to remember that Ziv is proud of - although not fully agreeing with - her race and how they do things. So for her to transition fully to female would be cutting off her most tangible connection to said race (aside from the purple skin, but if I had to bargain I would assume there are other alien races that have purple skin).
Her transitioning fully to female in solidarity with Raene would not work, first and foremost Ziv has no insecurities about her being hermaphroditic, from what I saw she fully accepts the way she is and has no issues with that part of her.
Second, Raene needing someone to transition alongside her doesn't seem to be the way the game is going, like I said before, the final characterization for Raene seems to be a pre-operation trans-woman accepting who she is, but even assuming that her final arc is her transition, it wouldn't make sense for her to gain all this confidence, learn to accept who she is more, and then turn around and need someone to do the operation with her. Her arc right now is heavily leaning on self confidence, it would butcher the character, and the progress made with the MC, for her to not have confidence going into something like that.