It would be fail of the century if he lost this draw before final.
You have to consider that that Benny played out of his mind in first 2 sets in Wimby. He cannot repeat this performance just like Rosol can not repeat his crazy ballbashing night vs Nadull any time soon. These are once in a year, perhaps even once in a lifetime matches.
Federer in easy 2 sets .
I think Federer will be able to step up and get rid of Benneteau in two close sets. Like you, I just don't see Benneteau able to play so well twice in a row against the current number one.
However, I think it's unfair to compare Benneteau and Rosol - one is ranked 32 in the world with a previous high this year of 26, the other has never been higher than 65 and is currently 97 in the world. Clearly Benneteau is more likely to play better more consistently.