I would make him develop a two-handed backhand to deal with Nadal's crappy moonballs.
Seriously, I would make Roger work on his backhand down the line ala Youzhny. Watch how the Russian can open up the court with ease with that one shot. Federer can hit that shot, it's in his arsenal but for some reason he prefers to just keep going crosscourt all the time.
I would stress the need for a high percentage of 1st serves, I mean 37% in the 2nd set and he won it! He needs to serve strong from beginning to end so that he gets plenty of cheap points.
I would hire Gill Rhys, Agassi's former fitness coach to take Roger's body to another level. He can get fitter and stronger, no question. This will also give him more confidence in those nerve jangling final sets to really let it rip. Then he can blubber with joy when he stuffs Nadal.
I think that are some reasonable suggetsions as well.
maybe Fed should hire us to coach him? we would push him to his well deserved GOAT status ;-)