Hearsz did mention that there may be an alternate scene for the twins on SubStar at some point. But they are very much "summer fun" gals where Sister and Ashley
might be long term gals. Remember this game will have separate gals for those 2 categories and that will change the approach to Lewdness, I am fairly certain. So while the twins may get special fun times, I would not have any expectation for Sis/Ash to get that (but it may not be ZERO
)
If it weren't for their rule for not sharing after one is chosen, it would theoretically be possible to share as long as they are not interacting with each other. Perhaps MrDots wants to be careful regarding the "P" overlords. To build a full "NSFP" version would require a lot of content, like the DM patch for Ecchi Sensei.
Obviously, MrDots couldn't create/authorize such a side project themselves, because it would get them trouble with "P." It would have to be done by an anonymous "Evil Modder."
I'm not sure if the extra effort to create these new combinations would be worth it. I think the I-patch does help the narrative, explaining some of the hesitance of S, helping Nichole to feel irrational in her fantasies (the worry that being worried MC is "getting busy" with an old friend is not a stretch). Adding extra combinations in lewd scenes would be very interesting, but not sure if it contributes enough to the narrative to warrant the resources and risk. I'm also reminded of how you can't keep everyone satisfied, over on the Treasure of Nadia thread, we have some complaining there is too much group sex.
But we can dream, right?