I’m nodding when I read how you consider characterisation more important than tropes. I’ve never been much into tropes, and the ones I could think of for the challenge were very character- and ship-specific (even situation-specific). For me, too, it’s essential to recognise the canon characters (in AU fics, too). But perhaps because my favourite characters (to write, and to a great extent to read, too) are not as central and so much present in canon as (some of) yours, I’ve felt that there are rather different possibilities for developing the characterisations, particularly a decade or two before canon era (where a big part of Marauder stories are set). There are popular fanon characterisations, which could be compared to tropes, I guess, and those can be subverted without going out-of-character.

Your own challenge is great. I’ll be looking forward to seeing the music books completed. And I’ll remember your post when I notice that I’m postponing any task out of fear.