A few other thoughts:
1. How long would it take to disassemble Flight of the Hippogriff and move it deeper into the Forbidden Forest somewhere so they could use that area as additional viewing space for the new Hogwarts/Forbidden Journey light show at night, and possibly as a performance space during the day?
2. I definitely see them building a full-fledged Madam Puddifoot's, perhaps where the Dragon Challenge entrance and lockers are currently? (See area outlined in black below.) This would keep them from having to remove that wall that separates Hogsmeade from what will probably be an extended Forbidden Forest.
View attachment 5020
3. I could see the exit from the Hogwarts Express leading in two directions, either directly into Hogsmeade or into the Forbidden Forest. This wouldn't result in a broader Hogsmeade area but it would double the amount of space available to Wizarding World guests at IOA. And unlike Hogsmeade, which can be get quite hot, the Forbidden Forest would provide lots of shade.
4. Universal is not going to remove or alter Mythos, and I think the Mystic Fountain will stay, too. But Poseidon's Fury could go and no one would miss it. Maybe the Eighth Voyage of Sinbad as well, at some point? How likely is it that Universal will ask Rowling to work something resembling Mythos and the Mystic Fountain into future episodes of Fantastic Beasts, I wonder?