I'd watch this senseless fight. Old GSP is a puzzle wrapped in a riddle folded into a tinfoil question mark (I know, question marks aren't even ranked, but they are DANGEROUS). I'm not sure how this one plays out, because I keep underestimating both fighters. I'm pretty sure Khabib doesn't touch prime GSP and would get jabbed teh deh death, but whatever.
I am sure it would lead to the most awkward press conferences and face-offs ever, though. Not a bad word would be spoken. Very hard for the Helwanis of the media to stir up any shit between these two.