I loved Atlanna in the movie so much, I'd watch or read a prequel about her story before she met Thomas Curry.
Like the show Krypton about Superman's planet and family before it exploded, but now about Atlanna as a young woman. I think there is potential for a great story. I think prophecies could work to foreshadow Arthur and Thomas Curry. Actually, Atlanna mentioned something like that when she was talking to baby Arthur in the movie about a future king who would rule like Atlan did.