There’s a lot of detective stories that feel like natural fits for an audio drama, or stories that could be modified into thrillers and such to compensate for the loss of visualization that audio dramas usually compensate for with twists and reveals. Audio drama is usually pretty heavy on monologues, expositional dialogue, and reporting and recall style storytelling.
Paul Dini’s Detective Comics and Streets of Gotham runs would be natural fits for the product, particularly with stuff like Joker’s reveal as the magician competing with Zatana, Abuse turning out to be Colin the kid, and Hush’s frequent retellings of his backstory.
Tower of Babel could work with the right take on its reveals and moments.
Geoff Johns’s Rogue Profiles would supply good work.
And I suppose a particualrly ambitious project could be something like Kingdom Come...