Having sex with other people is one thing but having an incestuos relationship with Haley is another thing. On top of that to expose that relationship to other just to have a threesome is not something I see happening in this VN. Look at how the MC reacted untill now to the feeling he had for Haley. If it was a normal relationship yes maybe but as it is now I just can't see it.
I get that people want a threesome with Haley but it doesn't make sense. Let's put it this way.
Let's say I see happening a threesome between MC his boss and the husband of Haley's boss because the black guy is gay and he gets along with the MC. It's just me projecting my fetishes onto the game it doesn't actually make sense (it's an exemple, I'm not into that stuff

).
On top of that there are enough games that deal with that stuff. Every other VN Ptolemy does has those things. Must they all be the same. Just play Alexandra. That VN's story is based exclusively on the exact same fetish. Why not play that? Why convert every VN into another Alexandra clone?