I always figured Fantastic Beasts could bridge the area between the Ghostbusters corner and the IOA Hogwarts Express Station. It could have dual entrance/exits, meaning you can only access with a 2-park pass (like Hogwarts Express, only you could exit to either park). North side could fit the New York area, south side fits the Forbidden Forest. They've got a parking lot back there that can fit a Transformers-sized ride, and knock down or utilize 2 soundstages and you have an area the size of Diagon that doesn't replace any guest areas. Or hide the Hogwarts express as a mid-century elevated railway, and allow guests to safely pass under it, and you have full access to the backstage land.