I think a Shazam! cartoon would be awesome. Especially in the age of Harry Potter and Ben 10, Shazam! would be right at home. Don't make it too silly, but still have fun with it. You'd need a sort of Genndy meets Timm artstyle for it. Take a cue from Jeff Smith and make Billy a *little* boy. You can have lots of magic monsters and he can also encounter heroes like Spy Smasher, the Bulleteers, and Isis. Billy could have a crush on her.
Billy could also do some traveling in order to find his sister Mary and he could have help from Uncle Dudley.
Sivanna could still be a mad scientist but he discovers that magic exists and wants to harness power like the Shazam lightening for himself and his inventions. I can see him doing something to free Black Adam thinking he's gonna get him to work as minion to which Black Adam quickly schools Sivanna and the master ends up the lackey. Kinda like, one day you're Lex Luthor then you do something boneheaded and suddenly you're Deesad.
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