Florence + The Machine would be perfect for this film. Their three soundtrack songs (Heavy In Your Arms, Breath Of Life, and Over The Love) are all perfection and perfectly written for their respective films.
I doubt Taylor will be on this, though, since she already has done two for THG, and she has a new record coming out right before, so releasing another song separately would be confusing.
But come on, Lorde, you better have gotten Queen Flo.
The performance of this, especially on Spotify and pop/alternative radio, could really be an indicator for how well she is going to do with this 2nd era.