No, that's true, given the central point of the game - y'know, the porn - I usually assume that any developments would have to be in either a romantic or sexual course, given that Jeremy is purely about the sexual potential, it just seemed obvious to me that any additional work done to him would be of either of these directions.
But I'm not personally a BBC-connoisseur myself, so I can't speak for that kink as a whole.
I'm still not sure why you think giving Jeremy the same as every other character has - personality - would somehow stand in the way of the BBC kink or his sexual potential. There is zero reason why it should, unless you think somehow people would find it disturbing or less fappable to understand a character outside of him shoving his dick into whoever. Or you think Jeremy will stop his deep-dicking session to have a deep and meaningful with Lena, blue-balling his fans.
Although... that idea is not half-bad...
Also, there are other kinks already at play in the game - like D&S - among characters that are nicely fleshed out, and not only does it not disturb the D&S, it adds to the appeal. The D&S kink is probably even going to have a bigger role then the BBC kink going forward, considering it'll likely play a major part in Axel's route, and possibly Seymour's route. If you're playing an Ian who is emphasizing dominant traits, there are already demonstrations of D&S play in multiple routes - Lena, Allison, Holly, Minerva (maybe others I'm missing).
When it comes to Minerva, there is a perfect example of how you can take a relationship based purely on sex at first, and then add in personality as you go. Somebody already mentioned this and made an excellent point with it (EDIT: it was
MyStupidPornAccount ). For example, we didn't know anything about Minerva for most of the game so far, besides the fact that she's a bitch and shows blatant favoritism for Holly while shunning Ian. It's only after you get involved with her that it starts fleshing out her character, showing she's a mum who has a rocky relationship with her nerdy husband and suffers from lack of sexual gratification.
And btw, Minerva is all about kink too - if you're into MILFs, public/risky sex, and the choice for D&S.
Sure, I get the idea, for that matter I don't think they are bad ones, but what would be the story purpose for these developments?
I could see something to do with Ian's writing relating to that sort of development, keep in mind that the point of Jeremy in the game isn't his own story, it's his role as an NPC that facilitates the fighting section of Ian's story and a specific kink to Lena's.
The same story purpose as events like the one where Perry, Wade, Ian and Jeremy watch the fight together at Perry's house. There's no sex there, but it does offer as an insight into the dynamic between the guys, and points out how awkward Perry feels around Jeremy. There are probably other events but that was just one that popped into my head.
If there was going to be an event like quiz night, or a convention, there's no reason why it couldn't operate the same as Ian hanging with his group at the pub, or Lena going to the club with her friends or whatever. The main focus of the scene could still be Ian going somewhere to hang out with friends and develop a number of relationships while there (and would help if Lena has been invited into their friends group at that stage). The reveal of Jeremy's nerdy side could be worked in alongside other stuff that goes on at the event, in my examples I was not basing the event specifically around Jeremy, but pointing out how the event could trigger the revelation of his character. With Ian and Lena there, it would also give the benefit of showing the particular moment from both perspectives, and how they perceive it with their existing knowledge of his character.
From there you could have Ian discuss it with Jeremy when they're leaving the convention/quiz, or if Lena has something sexual going on with him (but the player wanted more then just sex), Lena could have the option of questioning him about it or discussing it - eg. 'I had no idea you were into __ - you looked so happy!' or 'I had no idea you knew so much about so many different topics. That's really impressive'. Or alternatively, she could choose not to get to know him better and it would just be sex.
If Jeremy was going to have a transformation path, especially if he was gonna be romanceable, those interactions would serve that story purpose perfectly in Lena's path (and at the very least deepen Ians friendship and trust with Jeremy in his path, depending on how he responds to the conversation). I mean, whereas earlier that nerdy hobby or him being so smart alienated him, with a smart, creative and easy-going girl like Lena he could find someone who saw these aspects of his personality as good things. It would also serve to separate Lena from other girls, because she could be the first girl who he can feel he can be vulnerable around and reveal himself to.
And all without having to sacrifice the BBC kink.
You're right that it could be interesting, there is no reason why he couldn't have a variable like Holly that both Ian and Lena can influence, I just think that for Eva to seriously consider writing it, there has to either be a sexual or romantic hook for Lena and a story-related one for Ian.
For Lena you already pointed out the sexual or/and romantic option, which I mentioned above. As for Ian, it could be as simple as strengthening his friendship with Jeremy, especially if Ian and Jeremy have been very open with each other over their sexual exploits (including Jeremy seeing Ian with Cindy) and there's a
really good reason for Ian to keep things good with Jeremy if he doesn't want his relationships to end in a mess.
It's not that different from Ivy's position in the game. Technically she knows both Lena and Ian, has had content with them both, and is intimate (I think? I don't play the lesbian routes) with one of them. Her moments with Ian and his score with her could also mean the difference between her keeping his secret about cheating on Lena - like when she sees Ian with Cindy in that alley - or revealing everything and destroying their relationship at some point (is she's still very close friends with Lena).