Yes. There are currently around 4 Cindy paths and the issue with the epilogue is that it hurts the first two:
1. Ian helps Cindy and Wade: Cindy flirts with Axel anyways, helping Wade seems to be pointless.
2. Ian romances Cindy: Cindy flirts with Axel anyways, all the romantical build-up and the passion of Ian and Cindy during chapter 1-9 becomes moot, since Cindy may just fuck around anyways.
3. Ian fucks Cindy: Cindy flirts with Axel, this is "fair", since Ian doesn't commit to her and possibly also dates Lena/Alison, so Cindy isn't as loyal to Ian.
4. Ian doesn't help Wade and ignores Cindy: Cindy flirts with Axel, this is also logical and the expected result of that plotline.
The four routes you describe make sense, though I'll push for a different take on them.
Stepping back slightly: You said in a different post how Cindy in chapters 1-9 has more depth - you said, believable motives with relationship issues, chemistry with Ian. She's not sure what she wants in life but knows she wants more than the rut she and Wade have gotten into. I agree 100% with all that. But for me, who Cindy is in chapters 10-11 feels like a continuation, not a dumbing-down or turning her into a person unequivocally on the wrong side of things because of her potential cheating. She's been handed at least one, and maybe two, unexpected things she's really excited about which could change her life, if she chooses to really commit to them. The one hard-coded thing is Axel getting her the job with Wildcats. The possible second thing, depending on your playthrough, is a secret affair with Ian. (And further, that secret affair could be, from Ian's perspective - which he has to share with her at some point - either a casual fling, an aggressive sex-only relationship which Ian controls, or a hope for true romance.)
Taking the gig with Wildcats and flirting with Axel first (your routes #1 and #4). The variable is Ian trying to help Wade connect better with Cindy or not. But either way, Cindy is excited about becoming a model and unreasonably clingy with the guy who made it happen for her. That he's smooth-talking and physically fit is just who Cindy would go for; we're told at some point that's basically the personality and body type
Wade used to be, when they first started dating. She's chasing after a way out of what seems to her a boring life, and I think she's doing it the way her personality in ch1-9 would: she gets selfish and ignores Wade, she thinks she's trying to be friendly to the girl who lost out (Lena) but actually is coming across as a jerk, and in general she does her best to just coast through and focus on what's exciting to her without wanting to see anything negative.
You say helping Wade seems to be pointless but we don't know that yet, and maybe the point in those choices is less about the relationship between Wade and Cindy, and more about the friendship between Wade and Ian. It seems very possible to me that, no matter what Ian does, the overall storyline in ORS for Wade and Cindy is simply how they break up. And Ian trying to support them, or ignore them, is about the core male friend-group of the story: Ian, Perry, and Wade.
If an affair with Ian is also going on, I still see Cindy's behavior in ch10-11 as consistent with what we see from her in ch1-9. Say Ian sees her as casual or wants to demand sexual favors from her (your route #3). She recoils; she wanted a
positive change in her life, not more drama, and gets pissed off about it, whether she complies or not. So she falls back on her excitement about Wildcats and wanting to be around Axel.
Say Ian thinks he might be falling in love with her, and urges her to dump Wade and just be with him (your route #2). Cindy is excited, but nervous; it's a huge step, and irreversible, and she's not entirely sure it's what she wants, because it
would be a positive change, but it's still so much drama, and she doesn't want that. The Cindy of ch1-9 wants things easy, wants good stuff handed to her on a silver platter without having to make hard decisions. The Cindy of ch10-11, I think, has that same personality: she
doesn't choose. She avoids Ian and, when Ian pursues her anyway, avoids serious conversations with him as much as she can. So Ian's over here waiting on her (in between the mind-blowing sex, of course) and she's excited about becoming a model and partying with Axel. That all seems very like the Cindy we've come to know from the start.
Lastly, we don't know if Axel and Cindy are sleeping together, or "in a relationship," in quotes because whatever that means to Cindy, we all know it means something very different to Axel. It wouldn't surprise me at all if them having sex or not
is still contingent on Ian's choices, which is what you're saying may no longer be the case. Again, taking the idea of the primary story of Wade and Cindy in ORS being how they break up, this could be accomplished in the end through Ian, or through Axel, or it's simply that Cindy becomes a big-time model and leaves Baluart and everybody in it behind.
I think it's possible - even likely - that if Ian sees sex with Cindy casually, we'll find out down the road she's sleeping with Axel, but if Ian wants a real relationship with her, she's being a party girl, doing what she thinks models do, but isn't sleeping with Axel. If Ian ignores her and Wade, maybe she just becomes a successful model and moves away. And from Axel's side, even in the ch11 epilogue when he tells Lena he's not sleeping with Cindy, that too could still go either way. We do know he's a habitual liar, but he might also be telling the truth about Cindy, because maybe he's only fixated on Lena and couldn't care less about Little Blondie. Or maybe he's a fiend who belongs in one of those harem games as the big-dicked, asshole protagonist, and Cindy is calling him Daddy every night. We just don't know yet.