Making an adjustment to accommodate is exactly how you ruin consistency. Even a game of D&D has some rules, and a good DM will enforce them. A Lawful Good character who suddenly goes all murder hobo should find themselves running into major consequences, maybe of the type that could result in a player kill. A character who's supposed to be agorophobic can't all of the sudden be really excited about going on a camping trip. A slut who's slept through every tavern in Baldur's Gate can't suddenly be a blushing maiden, unless she's got acting skills, and a really high deception and rolls a 20, but then again, that would make it consistent again.
Well, no.
LG character turning murder-hobo changes his alignment. In previous editions it was actually written in the rules (don't know about 5e). If he is a paladin in older editions - he looses some powers. Or atones. The consequences are based on the tone, type and setting of the story, that unfolds, not on the rules of the system (in most cases... and where they were based on rules in the system, the developers realized it was a mistake). But in a game he would do that, because the developer pushed the story in such a way to send him on the road of chaos. Not just because.
No matter what the phobia, a lot of people decide to face it. They go trough the motions - and than ether fail or succeed in facing it. Since I can remember I have a phobia of cockroaches. Do you think I call the police, when I find one in the bathroom at 4AM?
A slut probably wont "just turn shy". She may if you drop 3rd degree burns on her, tho. She could be a blushing fest in front of the MC, because she finally feels something for someone.
There are ways to justify so many things. First thing my first publisher told me after reading my draft was:
"It need work. You have things in there for their own sake. Black dude is there to be a black dude. People use swords, so that you can have swordfights. Take the script and make the characters characters and build the setting in such a way, so that swordfights are justified. If you feel the need to have a specific thing - ether justify it or drop it."
I have yet to see something, that can't be justified in a story. This is why you plan for the story from the start. Why you build the setting from the start. And why you pick a style from the start. You can start the creation process with:
"This is the story of Mal Raynolds, a man of broken faith, rebel and father to his men"
Or you can start by:
"I want cowboys in SPACE!!!"
Both can lead you to Firefly. Both can lead you to ruin. That is on your skills.
Similarly a fetish has the power to completely change the tone of a porn game. I intentionally combined BDSM with the idea of a light hearted romance because BDSM has an inherent dark tone to it. It focuses on pain and humiliation. In order to keep such a tone light you need to give me a character I can believe that from. Sorry to make another anime reference, but Darkness, from Konosuba, is a perfect example of this. The show is based in a fantasy world that seems to operate on fantasy game rules, but is an actual realm with living people governed by the same gods as our world. In it Darkness is a Crusader, essentially a paladin, and a huge fucking masochist. She gets all excited when the main character calls her a pervert for enjoying being a human shield. She gets all excited at the chance to fight a strong or disgusting monster. She starts fantasizing out loud about how someone or something might have their way with her. By making her this over the top comedic character we can suddenly keep a light and fun tone in spite of a dark fetish.
However, when you do that too many times in the same story it stops being a story and starts being a collection of content to serve nothing but fapping. You see it all the time, games come out boasting 15 different girls who all have the personality of a cardboard box and each like something a little different sexually speaking than the other. You never actually get any sort of coherent story from it, its probably got less plot than your average porn. Why? Because you spread the story too thin to support all these different kinks and fetishes.
That's why you decide on a story first and then see what fetish content you can fit into it.
No, you get 15 cardbox characters, because the dev was lazy and never put the time or effort in making them interesting. Or they don't have the skills and creativity to do it. There are many ways to motivate people to do specific things. You just need to spend enough time developing that character, so that you can push them the way you need. You are the author, you created them. You know (or should know) everything about them - their hopes, dreams, fears, secrets... There is no such thing of spreading a story too thin. Problems can come with the pacing but pacing is more in tune with "I'm too good for my editor" problem. It's why we have editors, proof reader and knit group of people who read the early drafts.
This is why for a game and especially if you want a sandbox-ish, harem-style porn game you start with the content. Than outline the story and characters. Tweak whatever needs tweaking. And than start writing. We are not some woman giving birth to a child in a cave. We are authors. We are to the woman the genetic engineers slicing and dicing gene sequences to create our own perfect übermench. A story goes where we decide, however we decide, when we decide. And the only thing we need to do, when creating it is ask questions.
"Why?" - the question, that will make you make decent characters. Why are they that way? Why do they do that? It can literally drive a story. It will have the same effect on a setting. Why are there cowboys? Why are there so many rapists in this place?! It will fill the gaps in a story. Why is the Consortium out to get that character? Why can they deploy a full-blown tactical hit-squad?
With enough work, every hole, every inconsistency, every abnormality and every wish can be fulfilled. It's not about "spreading the story" but "Knowing my limits".
And, yes, there is much more to it, but on the base it's this. If you can answer the question - you can include it. If you can't - you won't include it.
