Funny Girl is a show that lives or dies by its leading lady. The show itself does not work if you don't have someone with a particular energy and star power - Streisand, Michele, Benko, and McCrimmon all had both.
I have not been Shankman in the role of Fanny yet. However, I DID see her as Elphaba years ago... I was not impressed at all. She may have grown as a performer since then, but based on what I saw of her in Wicked, I can't imagine her being more than a merely adequate Fanny.
"There’s nothing quite like the power and the passion of Broadway music. "