IMO, Leona and Lux should get some kind of lore connection at some point

Since they're both light-users, they could have such cute chemistry.

"How would they meet?"

Maybe Leona goes on a pilgrimage as part of a Solari thing, and crosses paths with Lux during her travels. Or maybe she even SAVES Lux, say, from a monster or bandits! (not that Lux wouldn't be able to defend herself, but she could get overwhelmed)

But that's just me fanboying, so it could go differently.