While we discussed a bit about our prediction for the first part of chapter 12, there wasn't as much discussion for part 2 by comparison.
I was negative about chapter 12 part one, since the main part about Ian on the beach was rather unspectacular, especially since Perry and Wade are among the least interesting characters to have there. A Lena section was smuggled even in Ians own part (and unsurprisingly less droll with a solid Axel scene) and the last bits with Ivy and Louise could've been build in everywhere, they didn't had anything to do with the vacation.
However, the first past had a lot of necessary setup that is crucial in the following parts, because now Ian and Lena can act and react as NPCs, because their positions have been enstablished:
(Bonus points if you have those on the same playthrough)
So what the next part should include:
Lena and Ian accusing each other of cheating (Lena can know of Cindy, Ian can know of Axel, Marcel and Jeremy) and possibly ending their relationship.
Lena, Ian and Holly discussing the trinity, since Ian responded in part 1 about his girlfriend Holly mingling with Lena.
Lena mingling with Emma. Either the two of them, which doesn't have much buildup, a lesbian fest with corrupted Holly (who already fucked Lena and Ivy) or Lena has a threesome with her boyfriend Ian and Emma, because the pair wanted threesomes and haven't done so aside from Louise.
The game Never Have I Ever can be the impetus to learn more about Lena/Ian cheating, as well as Emma being interested in Lena/Holly, if the questions lead to lesbian experiences etc.
With Lena knowing about Cindy and ready to confront Ian, it may also a opportunity to tackle on Wade/Cindy. The trip can end with Wade knowing about it and breaking up. A factor that was neglected for a while was Perry being suspicious of Ian if he didn't give plausible answers after he fucked Cindy in chapter 9 and 10. Perry and Wade may find out on the trip, if they have further evidence with Lena. They could also accuse them during the mini-game.
Considering that Ian and Cindy didn't progress after chapter 9 and were just fucking in chapter 10, 11 and 12, it shouldn't be no longer hold off. Cindy has to get influenced on the yacht on one way or another (not necessarily getting fucked but being further convinced to pursue that career) and she has to break up, possibly start dating Axel (especially if it is just casual with Ian) or give Ian an answer to his present/demand for clarity. If Cindy and Ian are still casually fucking in chapter 13 and still holding off everything, then the game is revealed to dragging everything out and not having a properly build up story.
Unless I'm mistaken, Lena misses the final days of the trip because of the next trip with Seymour. So I assume both tripes are included in this chapter (and not the epilogue), and it merely branches out.
Regarding Seymour, a repetition of a plain masturbation scene like in 9 and 11 and some basic modeling isn't enough. He can use her on a business trip as some sort of trophy woman, introduce her to others and get more clear on what he is actually expecting of her, since so far he is just content watching her spasm around the floor. Considering GGGB, I could imagine something like a sex club like with Keith or a business trip like slut Ashley and her boss, when she fucked potential clients.
Also, Seymour and Lena making a stop on the Wildcats yacht with Axel and Cindy is out of the question, I assume, or Seymour/Axel would have mention that. Could've been spicy as well.
If the epilogue switches back to Ian, it could show the conclusion of his breakup etc. with Lena, and may also get the Louise date. Best case Louise changed her appearance a bit and aside from fucking, they also discuss her job so that the plot isn't neglected and the rest of the game isn't just about fucking.