I thought of something crazy. If by chance the characters from Primagi returned in AiPri as an AU, not just Matsuri, but the other girls including the human form of the mascots to give an indirect continuity to Primagi since there was no S2. But I think they would probably use at most the 6 main characters because of the screen time.
I also don't know how they would mix the concept of the magical world, but I think the Yakuza from Primagi would be happy with that.

But honestly AiPri would be better suited to do a crossover with PriChan because of the theme, Mirai and the other older girls in AiPri would be interesting, but I don't know how they would do that since the characters are in a boarding school.