I don't think anyone hopes to see Federer in their draw, even now when he's older. There's still the possibility of him catching fire. Out of the other players in the top 4, I'd maybe say that only Nadal would prefer to have Roger in the semis over Nole, not over Murray.
The only options are Nadal/Federer or Nadal/Djokovic (or Murray/Djokovic, Murray/Federer) - in that scenario both would prefer facing Fed rather than Novak I think. Even if Novak could face Fed in the SF I think he'd prefer it to Murray or Nadal - both his last Aus Open matches versus the other two went 5 sets while he's beat Fed in straights on the Aus Open surface in their last 2 meetings. Just think on the slow high bouncing hard court Fed is at the greatest disadvantage.
It would differ if we're discussing clay, grass etc. - then clearly Murray is more preferable as an opponent than Federer.