I see a great potential for Duskmourn. Even it could be adapted to an action-live production, but a sourcebook would be mainly a monster compedium, or an adventure style "Saturday night in the hell". To be "playable" the lore should allow more opportunities to escape. Maybe in the future Valgavoth could be "defeated" and then other demons would steal part of "its" power to create their own "domains" style "ghost city", like almost spin-off.
Or there is a planar rift between Innistrad and Duskmourn, and then Valgavoth realises there are "unwanted guests" who can't feel fear in the same way.
I know this sounds totally crazy but I imagine a "micronauts-duskmourn" crossover. How? A group of humans don't survive, and then they are reincarnated into... action-figures. They are small but not the preys any more, and they want to help other humans to survive.
What if a native from Bloomburrow travels to other plane, would be changed the size?
Maybe Bloomburrow is very coold and fun, but the number of options for a long campaign is too low, because we only know the calamity beasts as antagonist forces, and a D&D setting needs a great variety of antagonist factions.