1. The concern of a "certain group of people" being attracted is them making mods that may sexualize the underaged characters.
Even if we made it that they're not even barbie/ken dolls and just empty undrawn space under clothing, someone could use other assets or make their own mods. The thing with this is that we'd A. feel violated that the rendition of the characters we made be used in such a way and B. If those mods get targeted by authorities, either F95's staff or actual law enforcement, it could put us in trouble as we'd have to prove that none of the fucked up shit came from us. It's something we could easily prove but it'd be annoying and if the police get involved we may get a take down notice from Marvel.
2. When it comes to Illyana specifically. The dev team as a whole feels the ick at the idea of Null knowing her at age 6 and then dicking her down at age 18. Veterans of our community are well aware of my distaste for Bruce Tim and him shipping a version of Batman and Batgirl where it was clearly stated Batman knew Batgirl before puberty.
Our solution for this though was simple... Null has no reason to be interested in meeting Pitor's 6 year old sister. He has college exams to worry about and if he's gonna hang out with Pitor it'd be at an arcade, not his sister's room.
Whether Magik makes it into the game, I believe 5 girls present themselves during the chapter she would appear in, I can still see Kitty and Pitor posting about her on social media just so it's not like "Oh hey Null here's my sister at random."
3. We have a legit following who actively want a SFW version of this game that they can show to their friends and family without being judged so maybe we could do "fandisks" like the Japanese do in release micro stories that serve as extended character epilogues. The dev team, and some of our community, has had interest in us tackling another property before making a direct sequel to TNH.
An example of what this would be would be like Null, Laura, and Gabby having a wholesome weekend eating spaghetti and renting a movie. You'd be able to customize your Null but other than that it'd be pretty kinetic.
This is still several years away though as future chapters are easily double to triple the length of Chapter 1.
Edit: 4. One of the actual concerns is payment services like VISA getting in a tizzy. Look up the recent news about Steam and Itcho. It'd be a fast track to getting us in trouble no matter how well we handle it.