I've often thought he could potentially headline. Whilst he's not really a currently recording artist, every album he's released (I think) was a UK No.1, so he's massive over here. He'd please the picnic chair brigade no end. His greatest hits setlist would have some great pop tunes in it.
The choice would be massively derided on here, but I think it could work really well for the festival - especially on locals day. I reckon half of our group would probably attend and - clashes dependent - so would I.