It´s not a problem of having enough power.When you´re dealing with such a huge franchise you´ll never have every freedom to do what you want. Plus sometimes you´ve got to listen to the fans. Imagine Peter Jackson doing everything he want with LOTR, it is not possible.
I think even Spielberg or Tarantino would come to their limits (that´s the only reason it would have been interesting seeing QT make a James Bond movie).
