I'd love to see Nilüfer Yanya sub. All her current dates line up nicely, last year's album was really well received and she had a good crowd in the Walled Garden back in '19.
Justice could be on the table? They're playing some European dates in August and haven't sold out their Ally Pally show in a couple of weeks.
I'm not sure Biffy/Fontaines is helped by a £90+ ticket price tbf. I agree BC aren't the draw they were back in, say, 2016, but it's still a premium rate price.
As for KoL, I saw them in Leeds last June as part of a pairing with Green Day in Manchester. Was a pretty good trip. Hyde Park would've needed a better line-up to tempt me to what historically has not been a first choice venue