Nancy doesn't need to be a huge star, so Samantha Barks will be fine.
Dustin Hoffman as Fagin. Fagin's music will be cut down to "You've Got To Pick A Pocket" and "Reviewing The Situation" both of which could be spoke-sung or auto-tuned.
Jon Hamm for Sikes. They'll cut "My Name" so Hamm won't have to sing.
Daniel Huttlestone for The Artful Dodger
If anyone ever tells you that you put too much Parmesan cheese on your pasta, stop talking to them. You don't need that kind of negativity in your life.