My suggestions may seem a bit random, but I would love to see Bella do any of...
- Owl City - Fireflies
- The Script - The Man Who Can't Be Moved
- Coldplay + Rihanna - Princess of China
- Justin Beiber - As Long As You Love Me
- Anything by Ellie Goulding
I also think Shiane should do songs that are a bit younger. Maybe Skyscraper by Demi Lovato or The Climb by Miley Cyrus - something that still shows off her voice, but is somewhat current and relevant to her age.
I've never had the words to say,
But now I'm asking you to stay,
For a little while inside by arms.
This old love - Lior
Agree on the Ellie Goulding it'd be perfect! IMO better than a Florence song for Bella. In saying that I'd also love Bella to sing No light, no light and I think if she sang Seven Devils it could be an amazing performance! Also something from Missy Higgins, like Everyone's Waiting or Peachy or something.
I really want Shiane to sing Valerie, I think it would be perfect for her in every way.
I'd love Sammy do a power ballad like Listen and then go edgy she could pull anything off with her vocal abilities though, there is no reason for her not to make the final. Nathaniel could sing grenade well, or something similar to that. It may seem strange but I think he could sing Somebody That I used to Know quite well also.
Fortunate their best performance was by far This Love, they need a performance like that again and you could really do it with any song. The Collective could sing something unsuitable and shit and still get through so it doesn't matter