If you want fic focussed on nominated characters with a worldbuilding slant, I'd request Any and put that in the optional details. Worldbuilding without OCs can be quite restrictive - "anything set at Hogwarts during the period between Grindlewald and Voldemore that engages with changes in Muggle society" is something you'd likely write using OCs (who may or may not be a Ravenclaw), for example a muggleborn student with a background that allows you to engage with the changes in Muggle society and how it affects the wizarding world.