You seem a bit obsessed with the butt how about the novel concept of the two of these sex bots talking to each other. Imho they should both be having vivid dreams about each other coming to a head when they have roofie/drunken sex after that the next day flashes of the act would slowly come to them and they should TALK after that.
Most annoying thing is how these two people as written don't seem like Father and Daughter more like hated ex-step father and step daughter who never liked this man who at one point in her life banged her mom enough to marry her. But now that she is being forced to be around him she is seeing him as a man
I wrote my suggestions based on the father/daughter relationship stage in the game at the time of my suggestions.
Making it clearer: Dad had fun touching and fondling his daughter's butt. No scenes where he was fondling her tits or pussy happened yet. So I used just what would seem a natural development for the following days in the game.
The 'rubbing' scenes I described could be substituted by oral sex scenes, or anal sex scenes if they made sense at that time in the game, what they didn't.
The repetition of the event as a tool to raise the erotic tension in the game is the important part of it, not the erotic act described, which could be anyone that made sense.
From my point of view time spent with dreams in a game is wasted time. Unless the dream reveals something important to the game plot (i.e. A supernatural being reveals the MC in a dream where he can find the key he needs)
Talking is of course an important part of the game. The main goal of my suggestions was to show that
if the game remained with just two characters it would not necessarily make the game short, or without many sexy events.
The game can last for years and a lot of sexy events can happen. All it takes is imagination.
I described three days (three months of game development) with the evolution of just one possible foreplay!
By the way, I love butt! But that's not the point.