I have now watched the Carlos Santana episode, and I agree that he doesn't look at Mark that much, which is weird, of course it was great to hear the two guitar legends play together, although Mark was just taking a back seat, which makes sense as Carlos was the focus of the show, Carlos can certainly talk though, but most of it was So Far Away from Mark's musical world.
The next series I would like:
1. David Gilmour.
2. Enya
3. Mike Oldfield.
4. Mary Chapin Carpenter.
5. Phil Collins.
6. Shania Twain.
I think you need people with a rich musical history to make the interview interesting and engaging.