So basically Michael can't beat rosberg in a neutral car that neither really like. If Ross Brawn thought that Mercedes would be better building the car around Michael then he would most certainly do that, the Ferrari years prove that. IMO brawn wants to build the car around rosberg as he as proven to be the better prospect for the team
Schumacher seems to dislike it more than Rosberg. Fact is the car is a turd (relatively speaking to the front-runners, a Kobayashi or a Petrov would love to have the Mercedes over their ride) and you can polish a turd as much as you like, but there is a limit and then you say, screw it.
Schumacher sees there is no point in polishing the turd and he loses nothing because he won't go anywhere else except retirement. Rosberg on the other hand has to, because his future stock is at stake.
Also Brawn isn't the boss of Mercedes, neither was he the boss at Ferrari, he does not decide whether a car is built around 1 driver or not. His role is way overrated.
And my opinion is, anyone who thinks Rosberg is better than Schumacher is waaaaaay out there, hehe. Put Schumacher in a McLaren or RBR and he wins races too, simple as that. Rosberg would too, so would Kobayashi and Petrov and Sutil.
It is the car that inspires the driver to do something special, not the driver inspiring the car todo something special.