Well, congratulations.
What is there now is amazing. Really, I can't stop. The set up and the promise of the previews drives me nuts. And I'm not an NTR fan (but I also don't loose my head about it. Most often I just don't care for it, sometimes it's titilating.).
In the game I'd like them calling him Daddy, Mom knowing about it (or learning about it and accepting, maybe after some persuasion), nice mind break scenarios, one of the girls a loving daughter and the other a sub and both cooperation and fight routes to be good. But I'm not sure that that would be the best direction, just off the top of my head what I'd like. You made something that normally wouldn't be especially interesting to me and I can't get enough. I hope you can continue that, whatever you have planned. Good luck
The only thing I'm sure about wanting, nay needing, is a not too slow development cycle. Don't torture me, bro ;-)
[edit] I think I figured out where the connection to my kinks is. Not that that explains all of my obsession, but at least it doesn't come out of nowhere. I always had a thing for the MC getting his friends to fuck their family (no matter whether the MC had them first, or if there is mind control or just mundane manipulation. And no matter whether the friend was in like that or was brought to it like the rest of the family). Now, the description doesn't conclusively say that the MC will become BBC's partner, if anything it points to voyerism. But the models and the characterization (loving daughter/sub) is good enough that a hint to that kink of mine is enough. I still think there is more, but above is a big part.