I'm starting to think that the options for a threesome (and even foursome) with Sage will be Maya and Josy. If you think about it better, it makes a lot of sense. Let me explain.
Being on Sage's branch and with the feelings left for Josy or Maya, creates a huge emotional burden and in the end everything may not turn out the way Sage wanted and planned it to be. She thinks of it as innocent fun, but she misses the fact with MCs feelings for Josy or Maya or vice versa. In EP9, we learned that both Josy and Maya think Sage is hot, the scenes with all of them - Sage's conversation with Maya and her kiss with Josy also suggest such thoughts. Sage knows about their relationship and that they are bisexual. It's just perfect material for potential drama for Sage's branch with a "feelings left" for one of girls.
While Quinn, in my opinion, is the least realistic option. In EP8, to get a threesome with Quinn and Sage, the MC must be on Sage's path. If MC is on Quinn's path at the same time, then she is clearly jealous, during the scene on the bench, asking how long MC has been fucking Sage. If MC chooses Sage at crossroads, then Quinn will definitely not be an option for a threesome, because she is clearly mad on him after, although she tries to hide it, saying that she doesn't care. If MC wasn't on Quinn's path, then a threesome in EP8 is still possible, but Quinn is clearly not doing it out of sympathy for MC, but just for fun and to show Sage exactly how she can have fun in the remaining time in college. Her dialogue changes during the scene. "I don't even like this guy," she says.
In another case, it may be someone more neutral, such as Lily or Elena. It is logical that we should have some choice. Because we can hardly refuse to have a threesome while being on Sage branch, so the girl's choice for it should be the option then. The limit here is the number of lewd scenes and I doubt that the DPC will make a choice of as many as 3 options only for the Sage branch. This is technically possible, but unlikely. Therefore, it seems to me that there will be two options and Josy & Maya are very good candidates.
These options and options for the development of events can work in the opposite direction. Sage and her fantasies have not gone away, even if we are not on her branch, and in Maya and Josy's fantasies Sage is in the first place. So foursome with Sage is also one of the options for the J&M branch. And, by the way, it is possible that there will be no choice between Josy and Maya on Sage's branch, but both of them at once, this will allow the lewd scenes to be unified for two branches simultaneously with minor changes in details and dialogues in them. In this case, the choice of J&M or someone else is already more real than 3 different lewd scenes. If we want to go for drama, we choose J&M, if we want to avoid problems, we choose someone else.
All these conversations at the party, on the one hand, could just be a drunken jokes and frankness, but on the other hand, all this was mentioned too many times. The only difference is in the chosen branch.
Jill and Bella don't fit in here. They have their own separate triangle or even a square - Jill, Bella, Bianca, MC. So, such segregation between MGs looks pretty plausible.
p.s. DPC mentioned some time ago about a very complex lewd scene he was worked on. What if it was a foursome? He had never made such scenes before.