Well, that would be nice and I don't mean this against LB in any way but as blues is generally a more improvisational kind of music, I just don't think that interests him and/or am not sure if the kind of mentality that goes along with blues would sit well with him since he seems to like things to be planned out and though his solos in "I'm so afraid" and the like do sound GREAT
...I mean, he "could" do it but I don't know if he would enjoy just getting up on stage unplanned and "jamming" in any real sense of the word so to speak, but that's JMHO and I could very well be wrong in my assumption on how he would "deal" with this.
Here's hoping the Mac do record a back to the roots album though, Stevie would sound great belting out some delta howlers.
John