Won't even think about Weird Al to be honest as he'll be too expensive.
As for Vince diCola and Stan Bush... I can't really see either of them having a lot of appeal unless they took to the stage for a concert. I don't see them being able to offer much in the way of a Q&A panel that would appeal to more than a small minority of the attendees and - without trying to sound too harsh - I've seen a recent video of Stan Bush live at Botcon back in 2009 if I remember right, and the years haven't been kind to him.
Sadly, performance wise Next Of Kin did a much
better job of all of his songs when they attended AA2009 than he did.
Auto Assembly 2012 - Bigger, bolder and better than ever!