I think Brawn feels he would be better utilized if he spent more time at the factory. He has sort of hinted at this. I expect him to step back into the technical head role. I expect Schumacher in time to fill the CEO role. Maybe Jock Clear will step up as team head?
As for the F-Duct... I don't know how much there would be to gain with a passive system. It would be very hard (I'm guessing) to stall the wing at a specific speed and then quickly reattach the flow when the speed drops. I think teams would have gone this route if it was easy to do. You get rid of all of the ducting and extra mass on the car needed for such a system. A passive system would more than likely acutate much later on the straights than you would want it to because you wouldn't want the thing stalling on fast sweeping turns either. Probably the main reason why teams go with a cockpit actuated system. They can actuate it as soon as they are chugging down the straights.
The Merc system is driver actuated, like all of the other teams. The main difference between the different teams' systems is where on the rear wing it blows.