The walkway is already there- it's the existing sidewalks behind and in front of the BC.
The trees aren't much of an obstacle for the Epcot view. We'll be able to see the Illuminations fireworks as well as SE and the HISTA and Imagination pyramids. All they block are the backstage areas which aren't all that interesting anyway. The rooms on the back side of BC have had the same view since the resort was built.