I think this is a good idea, and an interesting approach to twisting the world of Little Nightmares (I'm also a big fan of the franchise too). I think the base of the game is good but if I wasn't told it was based on Little Nightmares I'd have never known. In find a way to either flesh out the horrors or the way the player must survive and hide. Perhaps bringing in recognizable aspects from the game - the gnomes. Sausages. Bread. The strange localities (Can I have a farm on the roof of an abandoned building? In an overgrown greenhouse behind an asylum?) are a goldmine too. And remember, if you don't want to add anything to the mechanics these are things that you can provide for the player in the form of tips or example writing.