^ I agree. A period piece superhero in an era we've never seen would be great. Most modern movies are set in the present day and we've had 30s-set ones like the previous Phantom or The Shadow. But that's really it.
I suppose you could count the likes of Zorro & Robin Hood as period piece superhero movies. But with The Phantom you can set it in numerous eras that haven't been seen onscreen before in a superhero movie. Why not take advantage of that to distinguish your movie from the herd?