I'd love Sam Fender but yeah I reckon he's too big, rumoured for Glastonbury as well I think.
I was thinking Wolf Alice, Blossoms, Phoebe Bridgers, Brandon Flowers, Lily Allen could all be Obelisk headliner shouts but honestly I'm struggling for names a bit. Would love CMAT but I think she said she's taking some time off. Maybe Jungle could be a shout but they've moved away from a dance headliner seemingly.