I dont know how they would do it. I wouldnt be posting on this site if i did, I would be desiging it for another team now!

I think there is a an area of bodywork that could be used as part of the diffuser, while still conforming to "bodywork" regulations. This would circumvent the diffuser regs.
My line of thinking is very simple indeed, would a team that had the best iteration of the diffuser in 2009 simply sit on its hands and re-use it? Or would they push the boundaries to as far as they could possibly go?
What would Brawn do? We know his track record after all, so while it may not be a miracle diffuser, I expect it to improve the car.
I could be wrong, but these dudes dont get paid big dollars for nothing.