It would be cool to explore new and more varied minigames, especially given the relatively limited control design. An easy one would be a "Simon" style follow-the-leader minigame where the player mimics a series of slaps that gets longer and more elaborate each iteration.
Also looking forward to more panties and stockings designs in the future, and especially skirts!
How about a "shuffle" button that randomizes skin, panties, stocking, and size? Once the current ass is sufficiently smacked the next ass comes to visit.