Did Riot miss an opportunity to make a Zac skin?

I'm still hyped for the Shurima Event. I just find it odd that Riot didn't take this chance to make a "Sand Man" Spirit of the Sands Zac skin. That's just me though cause thematically I see it working with his skill set and passive. Maybe making a Zac skin is much more difficult to make than we thought. Zac currently has two skins (classic and special weapon) that aesthetically resemble gelatin and/or goo. If Zac were too get a new skin would it represent an element like fire/lava, water, sand/mud?; would you think they would try to put animations on top of the skin similar to Xerath's body energy particles? or maybe even leaving particles behind while walking similar to Kassadin?

I don't play Zac but if you wanted a new skin for Zac what would it be? What are your thoughts on Zac?