... Who would it be? Who do you think would have the most to offer and why?
I'd probably choose to take some lessons from Brett Garsed, because he is pretty much one of the best technical players as well as musical guitarists that I know of. I'd love to learn some of his finger picking techniques and his approach to chromatic improvisation. You guys?
Brian May. How to write "singable" guitar lines and create effective "guitar orchestras" and lead lines.
Plus, the whole Brighton Rock Solo thing with two delays is crazy... learning how to approach that sort of writing would be a lot of fun.
Also perhaps Slash, since he's got a great sense of how to "push" and "pull" notes in a line and in a scale to achieve really, really memorable solos.