first off, dave isn't going to die. his shirt is red because that is the color he's associated with in homestuck. furthermore, i'd like to happily inform you that red is the command color in official TNG, not the expendable ensign color.
okay. now. there seem to be more than a few people who are dissatisfied with my character transpositions, specifically, terezi not being jordi. i know, i know, they're both blind! she should have the visor! "same blindness!" "same blindness!" insert the entire "same ___" comic meme here.
i felt, and still feel, that her personality, talents/skills, and relationships to other characters fit much better with troy's character. if you think she should be jordi just because she's blind (i don't feel that there is no legitimacy here -- the ways that they handle being blind are vaguely similar -- i just feel that more significant weight rests with other factors) that is your prerogative. go forth and make your own star trek au.
i have lovingly prepared a more in-depth explanation for those who wish to read one (i've even capitalized it! just for you).
(Gamzee/Terezi wasn't canon or even strongly hinted at in the comic when I made the AU, which is why he's not involved in any way. I seem to recall thinking that he would be Gainan for some ridiculous reason. Probably something like "chill out, have a pie, tell me about your troubles." Karkat and Gamzee's relationship? No idea there.)
So who's Vriska? Can't have a Terezi without a Vriska, even if Vriska's dead and it's a living-characters-only au (which I haven't really specified). This is an issue that initially worked against Terezi's characterization as Troy, in my mind. The rivalry between herself and Vriska is a major part of Terezi's canon character, so she can't be completely left out of the AU. But there's an interesting solution to this! Troy and her mother harbor an intense and occasionally antipathetic rivalry, from what I remember. Obviously Vriska is not Terezi's mom, but a familial type of relationship between them as sisters has been mentioned over and over again in canon. Vriska's manipulative methods and abuse of psychic powers with "good intentions" are a surprisingly good fit, as well as the atmosphere between both sets of women being one of "their own little world" that only they are really capable of inhabiting. Even being dead sort of works in Vriska's favor, since Troy's mom only shows up like once per season but she still has a large influence on Troy by virtue of having been close to her in the past.
Another character that there's been question about is Rose. In my mind, Rose is a smart, kind of hilarious, reasonably objective, medically-minded individual (she psychoanalyzes her friends and has a book on the anatomy of the zoologically dubious, lmfao) who seems to be a shoe-in to marry the captain (though she doesn't in the series, save for the series finale when she's shown to have been married to him in an alternate future timeline). Rose and John also have a joint "daughter" in Casey, who parallels Krusher's son Wesley who more or less sees Picard as a father figure. Also come on, Casey = Wesley is as hilarious as it is bizarrely fitting. I have not picked a specific role for Kanaya yet, but I imagine she'd be a nurse in sick bay. Her own skills (midwife for an entire alien species, self-trained amputation surgeon lmfao also hey stitching bodies isn't too different from stitching clothes) qualify her equally well for such a position.
The only character I'm still really deliberating over is Data. The obvious choices would be either Aradiabot, Jadebot, or Brobot/AR. Jadebot would be awkward, because a) she's essentially another Jade and b) she is not autonomous without Jade. Brobot doesn't interact at all with the beta kids' timeline, in stark contrast to the other characters. Since Dirk is Spock in TOS, I could call it a throwback, an android modeled after him, but Data wasn't modeled after Spock; he was modeled after his creator, Dr. Noonien Soong.
Aradiabot is probably the best choice, because she is both in the right timeline and has some similarly circumstantial personality traits, including a sudden transformation to having "emotions" as when Data chose to utilize the emotion chip he'd been saving. However, I had two main qualms with this choice. Firstly, a main facet of Data's character is his desire to become more human, while Aradiabot didn't seem to give much of a fuck until she went godtier and became alive again; Brobot/AR would be a better choice to parallel something like this. And secondly, while Jordi and Data are best friends, Jade and Aradia have very little canon connection.
I could potentially solve the latter problem by choosing Sollux to be Jordi instead of Jade. He's techy and I could give him a half red/blue visor, but he's also less scientific and even less friendly, much more standoffish and sarcastic. Over all, t's a tough decision and I haven't made it yet; that's why there is no Data character in the original picture.
So! Hope that explains things a bit. I've been putting off addressing this for as long as i could stand to ignore the comments in my notifications. It's been more than a year haha, I think I did pretty well. It's only when it goes around again like this that the comments start popping up again.
If anyone would like to discuss this with me (politely! please don't just say "it's all wrong" or "make terezi jordi lol"), do feel free to send me a message! I'm not sure how much more I'm going to do with this AU -- certainly very little right this second, with so many other things on my plate -- but I would love to flesh it out a bit better even just for the fun of it!