I've always been into orchestrations and I'm lately falling in love with the rounded warmness of the cello. One of my favorite songs with noticeable cello is 'How Glory Goes', where the cello has a really interesting line even throughout the verses, not to mention the really moving part it has during the reprise of the call. I also love the cello in 'The Next 10 Minutes'.
Two of Billy Porter's songs in Kinky Boots have dominant cello parts..Not My Father's Son and Hold Me in Your Heart. Also, in Matilda, Quiet has a beautiful cello arrangement.
The Godspell "Yellow Album," the National Tour Cast Recording, features an acoustic/electric cello as its lead instrument, very prominent in most of the songs, particularly "All Good Gifts."
I've forgotten- what song was used in that dreadful revival of ONCE UPON A MATTRESS that had that lame business of an on-stage solo cello starting to smoulder?
Of course, Spring Awakening! The cello in Quiet is beautiful. Adding to my list: The I Love You Song, The Beauty Is, and in the Overture to The Light in the Piazza, at 1:52 starts a cello duet that is simply perfection.
The whole score of Spring Awakening is very cello-heavy and it's really beautiful. I also love the cello parts that Tom Kitt added to some of the songs in American Idiot when he did the orchestrations for that show.
Since you're interested in orchestrations particularly, the Doyle Sweeney Todd took some songs that were not normally cello-heavy and re-orchestrated them to be so, since both Johanna and Anthony played one.
Art has a double face, of expression and illusion.