Here's a great video of a Jack White's performance at Lollapalooza where he brings Robert Plant up for The Lemon Song!  

Now, if you remember correctly, Jack White was in the documentary "It Might Get Loud" alongside The Edge and Jimmy Page.  I'm not saying he's got the pull to get those two together for a Led Zeppelin reunion, but having an ambassador sent in to talk some sense into them couldn't hurt!