Keep Emma Watson as Hermione!
Replacing Emma is like eating a peanut butter and egg salad sandwich. You would be ruining a good thing. Harry Potter would never be the same. So, keep Emma Watson, and make yourself a good ole peanut butter and /jelly/ sandwich. Plus - Dan and Rupert would probably be upset. They have been working side-by-side with Emma for years. I couldn't bear to see an unhappy Daniel. That would break /my/ heart.