I voted yes. I'd like to see such a product that was set entirely in the Underdark. Have the beginning 1st-level characters with no experience dive right underground. While this would share some similarities with a dungeoncrawl, it would be more encompassing since it would deal with the entire Underdark ecosystem, political systems, cultures, etc.
In other words, what Night Below should have been.
In other words, what Night Below should have been.