Have you considered taking a look at asgardeventide? We have aged-down characters (such as the Marauders from the Harry Potter verse) and a Renly, Stannis and Joffrey to make Robert's life hell, alongside a whole tonne of other ASOIAF characters (Arya, Barristan, Bran Stark, Jaime, Daenerys, Jorah, Loras, Margaery, Oberyn, Robb, Viserys and Ygritte). We have a test drive meme going on right now, too, if you'd like to maybe poke around!