I never could imagine a French player playing Nadal-style anyway.
But the usefulness to "substitute" for Nadal is then highly questionable. I don't think Roger struggles with Verdasco-style play.
I don't think it's purely Nadal's style of play that troubles Roger. It's also his lefty spin, especially on the FH and serve, and it would definitely help practising with a lefty who can generate similar spins.