Adding genitalia, or indeed TF'ing the player in any way without direct player control, is pretty much the single most negative thing you can do in the context of TiTS aside from applying a potentially save-ruining thing like Bimbo perks. Look at Doc Badger for why forced/player-independent TF's are fucking awful. And yeah, everyone knows Badger's content "warns" you. It doesn't say "Hey, the damage done by this choice is irreversible, instantaneous, and will modify every single aspect of your character."
Somehow managing to lose to a cunt snake on accident and having them forcibly TF your PC would probably be very controversial as well if it could actually happen with any kind of regularity, because removing them still takes the PC's tails away, which can be a real pain in the ass to get. As it is, cunt snakes are the literal weakest enemy in the game, and even at level 1 you have to try to lose to them. And most generic mob encounters are like that as long as you're the appropriate level.
These kinds of TF's are exclusively for people that are interested in them and literally no one else (which is how most content is, realistically, and there's not an issue with that until it's suddenly injected into normal game flow as opposed to limited little niches). Yeah, there's some Badger fans out there that love her stuff, and I'm one of the weirdos that likes cunt snakes enough that I wrote a way to consistently and voluntarily have them glued to your butt, but unless SSTD's are limited to one little corner of a planet as a kind of "kink showcase," I see a lot of issues with them.
If we prop up the idea with a bunch of rules like "minimum duration" or "limitations of scope" to ensure that they're not annoying negatives that players encounter only on rare occasions, then what we're left with is, as I said in my last post, a minor annoyance at best. If people want to write something that forces the majority of PC's to run back to V-KO and spam their way through a menu every 50 or so generic mob fucks, fine, but that doesn't sound like a good idea to me at all. Especially on bigger planets where backtracking is going to be significantly more involved than little Mhen'ga.
Lowering one stat but raising another still has the possibility to be wholly negative based on context. "Oh, it lowered Intelligence but raised Physique? Good thing I'm a Tech so that's literally just a pure negative!" And I didn't think I even needed to address the idea of them being buffs. I mean, maybe Fen is okay with that idea, but it wouldn't line up with his current stance on TF buffs, and would lead to min/max situations along the lines of "Gonna go take on Lash. Better go fuck (x) of this generic mob to get that STD that buffs my stats before the fight!"
Also, though, if we're limiting SSTD's to only minor things like stat tweaks or cosmetic blurbs, where does the sexiness come in? Again, my understanding of SSTD's was that recklessly fucking mobs would give the PC diseases that TF'd them over time, which has a ton of appeal for its intended audience but is unavoidably invasive and irritating to players not interested in them.
*sigh*
I'm doing that thing again where I just rag on an idea and point out why I don't think it can work. Let's change lenses here. How can we make SSTD's work while keeping them as full-bodied bits of content that appeal to those that are interested in them and minimizing their impact on disinterested players?
My only real idea here is making them a planetary gimmick for a side planet, like Uveto's need for heat packs and whatnot. I could see the concept of SSTD's working if the PC goes down to a side planet where almost every bit of flora and fauna relies on infection or parasitism or whatever to reproduce. So like, when the PC lands, they have the option to pick up a UGC HAZMAT suit and explore the planet without worry, but losing in combat or taking it off to fuck the native species is an obviously terrible idea that holds an obvious risk of mutation and/or maybe even a Bad End if they go too far. Players could justify the actions of their PC by being too damn lusty for their own good. I know the "bad decisions prompted by a lust-addled mind" kink is a pretty big part of this kind of stuff.
The PC could also have the option to not take the suit at all, and be constantly exposed to the planet's mutagens if they just want to say "fuck it" and dive wholly into the content. Gating it would be pretty easy, as you could just have a New Texas style "gate check" if Steele tries to leave whilst infected with anything. You could be forced to get disinfected and cleaned up before being allowed to even get on your ship, easily and logically preventing the spread of the infections to any external NPC's without the need to "handwave" or flat-out ignore them, and you wouldn't even need to bring the Deus Ex (nano)Machina into the equation.
This would also have the advantage of allowing any NPC's written for that planet specifically to explore the implications of SSTD-style content in a controlled environment, so to speak. Maybe there's some adorable and naive UGC scientist girl on the planet that the PC can fuck, inadvertently infecting her and turning her into some sexual monstrosity when she doesn't cure herself. Or maybe the infections are more benign/goofy and she just grows bigger tits and a cock or something. You could gate it even more by only allowing the PC to access whatever settlement is on the planet if they're disinfected, limiting the NPC's that could engage with the infectious TF content to only the NPC's "out in the field" or whatever. A game environment built specifically around this kind of content gives everyone, coders, writers, and players, the most amount of control over how to handle such potentially controversial (but very appealing, for the right people) content.
The issue I see with this idea, though, is that it's not really "SSTD's" anymore. It's just a theme planet based around infectious TF's and statuses. I feel like they'd target the same audience more or less, but they are still distinctly different ideas. There's also the issue that this would be a whole planet devoted to this kind of thing, but this is all hypothetical. Maybe it could just be an area of an existing planet. Maybe a zone of Mhen'ga could be roped off for this kind of content and reserved for later levels. There's a lot of ways to approach it, but the persistent issue is that it's still not really "SSTD's."
SSTD's, to me, feel like something that needs to be a galactic constant, just like actual STD's are in IRL sexual encounters. You always need to be worried about STD's if you're having any amount of casual sex in the real world. Honestly, they're a really unsavory element of real sex, and that's one big reason why I don't understand the push to try and sexualize them. STD's are terrible and overtly disgusting things, especially when you get into the seriously fucked up territory of things like HIV. The entire notion of "Sexy Sexually Transmitted Diseases" seems like an oxymoron to me.
Honestly, I feel the kinks they would cater to don't really need to be tied to the notion of an "STD" at all, that doing so might turn off people otherwise interested in the content just based on principle, and that the idea of them being "STD's" adds needless complication to the premise. So the TL;DR of this is: There's definitely better ways to do what SSTD's would try to do. Ways that would make both the intended audience and those that are disinterested in the content much happier overall.
I don't have this kink at all, so I could be off-base here, but I can't imagine someone getting off to the idea of a highly-sexualized infection not wanting to try and spread it around. It has some elements of corruption going on for it, as well as forced-TF'ing if SSTD's are done in a certain way (more on that later).
