There are quite a few Kander and Ebb songs I think Guy could do justice to. "Sometimes a Day Goes By, as DR Stuart mentioned, would be great for him, and so would "Seeing Things" and "I Don't Remember You," both beautiful ballads from THE HAPPY TIME.
And may I suggest, should Mr. Haines choose to record "Seeing Things" that he include the verse? Although I adore the Sexiest Man Alive's recording of it (produced coincidentally by Mr. Haines' very own producer), he leaves out the verse, and the song loses some of its depth, because the chorus doesn't tell us
how the couple's ways of seeing things differ--the verse does:
You say, "Come down, you're going to fall."
I say, "Go up, you're touching the sky!"
That may not be quite right, but that's the gist of it.