The Rietta gangbang is going to happen eventually since Amor intends for her to be this AV idol. However, I'm hoping that her "fall" scene will be just her and Amor. Like Rietta may be an sex idol for all men in the kingdom, but to her husband Amor is when she'll do wilder things for. him alone.
Also I'm looking forward to how much their personality will change after all three of them have fallen, especially towards Kurt. From what I recall, the affection meter will drop significantly towards Kurt. Arika is embarrassed to be childhood friends with him, Rietta is now "phobic" towards Kurt or more specifically men with small dicks, and Terena is dissapointed that Kurt failed as a man to her and wonders what she did wrong.
This emotional damage is going to be so good, especially the remaining scenes before we reach the ending.