He'll do just fine in the official job description - managing the President's schedule and who sees him, overseeing the White House staff, etc...
When Obama wants a message delivered to Congress or his appointees in no uncertain terms, Emanuel will deliver it in more than no uncertain terms.
Whatever "authority" Obama cedes to him will be unquestioned.
Yes. I don't see where people are reading deeper motives into this choice. Rahm is simply the best guy for the job where the job is getting sh!t done Obama wants done.
The psychodrama of the last 16 years is over. New psychodrama will take its place, but not yet.