I don't think anyone wants to hear more words/statements/announcements from Brawn. It's time for actions and fulfillment of promises made in the previous years, and he has failed miserably in that. Norby already got canned, Ross to follow?
And no, I don't believe that he would be useful in McLaren. The team needs to move forward, not hire a 60 year old guy who has retirement at the back of his mind. They need a younger, more determined and more energetic man to help them replace Red-Bull at the top of the sport, and most certainly, Brawn is not that man.
Now at Mercedes, there are really too many "cooks" and someone needs to go. That is unless they truly have 2 different teams working on W04 and W05 but then again, who is going to be in charge of whom? If Paddy Lowe really signs for Merc, what is his role going to be? What about Elliot? Willis? I don't know who is responsible for the hirings/firings of the team but they have a lot of work to do to make this hierarchy work.