If we assume that no exclusive event can be triggered (which is reasonable, given that sel has said and reaffirmed that it will be possible to have a single PT that hits all events), that means that none of the other choices can trigger an event. And I'm pretty sure that that means that none of them will trigger a sex scene, because:
1. Sex scenes are replayable in the gallery as events with "neutral" variables, which means that a conditional H-scene hidden inside a mandatory event is not easily worked into his current system,
and
2. Sel likes punishing people who play LiL for the porn value, so blueballing everyone who requested an unrealistic 3some would be entirely on-brand. This idea is supported by the current update, where Yumi reacts to a 3some suggestion exactly like you would expect her to and we will likely see more of the same from the others. For example, we'll probably see Rin say something like "lol no way, a 3some with my former crush would destroy my relationship with Otoha" (which is exactly what you'd expect her to say).
My guess is the Chinami option will come back in the form of some abusive dialogue forks but not anything substantial.
Technically, there's already been exclusive events. The events just share the same name and don't get crossed out no matter which one you get.
'Getting Comfortable' in the Chapter 2 Main Events, completely changes depending on who gets Sensei based off the first Dorm War:
And each version comes with exclusive scenes and lore you wouldn't know about otherwise.
The threesomes could also simply be mentioned or implied, but not completely shown, like a few "sex scenes" have been, and therefore not replayable by themselves. You'd have to replay the event, that the lewdness shows up in, to see them again. Like with the recent
Sana and Maya stuff and the stuff on the computer
in the recent puzzle if you even wanted to see that.
But yeah, it'll likely just be extra dialogue with maybe some exclusive scenes that don't matter that much, like with
Yumi so far.