Thats a ton of capacity they's be losing. They certainly could replace it with multiple rides, but what exactly would they do?
I think the great hall restaurant would be a must, not that it replaces ride capacity, but it does tie people up and would be the biggest draw left that they haven't done. It would need to be huge though. I think they'd have to move the hippogriff though as I don't know they would want to have the great hall separate from Hogwarts.
As for the rest, I just don't know that forbidden forest is full of ideas for rides. A dark ride I guess? But a coaster through the woods? Eh. I love the idea of a coster through the woods from a ride aspect, but as a HP themed ride? Not sure how that fits. And even a dark ride would be too much like FJ IMO, just a flythrough hitting major scenes from the movies. I think a Quiddich coaster like the tron coaster could work. They could theme the cars to brooms and have you fly through the stadium. I like the shrieking shack idea, but again, what kind of ride does it lend itself to? I think a tri-wizard tournament ride is doable, but it runs into some of the problems the other ideas have. Just not sure how many great ideas are left for that area.