I just saw a TV show tonight called Death in Paradise with an actress who would be great for a younger Storm. (The show has been running for ages but I only just saw it!)
Her name is Sara Martins, she is a French actress and so speaks with a slightly exotic accent that also made me think of how I imagine Storm to sound.
Here she is. She's 35 but doesn't look it at all...
Batman v Superman 6/10, Captain America: Civil War 7.5/10, Deadpool 8/10, X-Men: Apocalypse 8/10, X-Men: Days of Future Past 9/10