It doesn't have to be a fandom I've written in before.

I don't suppose I could ask you for a crossover between Dunkirk and The Charioteer? You'd think it would be a shoo-in with both Laurie and Ralph's backstories, but so far AO3 does not provide. Any choice of characters. If left to myself I would probably do something pointless like introduce Alec to the shivering soldier.