Another Skin Concept

well, there is infernal diana there too, so I'm not sure how one would differentiate from the two.

The honest reason I believe that this simply wouldn't work is because even their kits are very much Sun and Moon in appearance and theme.

It wouldn't really make much sense for Leona to seem to call down a beam of Moonlight as her ultimate.

Or to see Diana throw a crescent-moon shaped Q and holding a crescent-moon shaped scimitar (khopesh), and claiming to be in reverence to the Sun.

(However, you could always make the argument that the Moon gets it's light from the Sun, ... So in a way, she already owes reverence to the Sun.)

I would like to see it happen regardless of my logic telling me that it doesn't make sense, but I'm not holding my breath for it.