Lot of good options. I also concur with the Winehouse, Bublé, Gaga and Lana del Rey picks.
As far as Winehouse goes, they did have a meeting with her about doing a Bond song for "Quantum of Solace." However, she was going through turmoil in her marriage / relationship with Blake Fielder-Civil, and she wasn't in the right headspace to do it in the end. (This is from the Amazon Prime documentary "The Sound of 007").
Ed Sheeran almost got the gig. He did have a meeting with Barbara Broccoli about doing the song for "No Time to Die." But that was when Danny Boyle was going to direct the movie. (Boyle previously directed Sheeran in "Yesterday", the Beatles jukebox-musical rom-com, so that's how he probably was in contention).
I'll throw in Whitney Houston. A powerful voice, and it would've been amazing if she and David Arnold had done something together.
I wish they'd give k.d. lang another Bond song too.
Speaking only for myself, I don't think the band would have been a good fit, and I say this as someone who's been in a Smiths phase for almost 40 years.
Laura Branigan, Heart, Pat Benatar comes to mind. I agree that Elton John and Queen would have been excellent. I think Dionne Warwick (giving her another shot after MKKBB) would have been an excellent choice for You Only Live Twice, Dusty Springfield for The Man with the Golden Gun.
But I think the question should be "Who should have been allowed to perform a Bond Song?"
There are lots of great singers/bands out there but who would you want associated with a Bond theme song? Literally forever?
And I think the songs are better when there is the slightest (or maybe not so slight!) nod to the audience that they're taking the audience on a journey.
In that regard I believe three of the five songs for Craig's movies fail in that regard and two of the artists/pairings should have never been let anywhere near a Bond song. And taken far too seriously almost to the point of depressing!
Like the movies, they can be a bit like wine - some age well and some don't...
All in my humble opinion - and as I've said several times, why not have another instrumental?