I think I am just looking it from a UK point of view, that order would make sense here.
You might be on to something though, NIN before Kings of Leon would be pretty good
For British acts (or acts with close ties to the UK) then headlining Glastonbury will always be something people want to do.
You can earn peanuts at Glasto and silly money in stadiums - happily doing both in the same year.
For global superstars it does not hold the same appea.