I can't believe no one came up with this:
Sequel name: The shadow 2: The shadow nose <snorting sound>
For a move that starts in an opium den, we should at least consider it all being a hallucination. Instead of being a confounding film, what if it was a masterwork in inconsistent narration? So The Shadow 2 would only be objective 3rd party observation with The Shadow 1 playing picture-in-picture.