Joseph Sedley Vanity Fair
I have been reading Vanity Fair and I think Joseph Sedley would be a great part for James Corden. (Mary Jones could play Mrs. O'Dowd.)
Joseph Sedley is overweight and perhaps is in his late 20s so the basic parameters work, no problem. More importantly, Jos Sedley is inherently funny.
You'd have to find pretty girls to play his sister Amelia and her friend Becky Sharp, but that's easy enough. You wouldn't need to do the whole book, just the first 175 pages. You can end it after Joseph bolts off thinking that the English were losing at Waterloo.
It would write itself, I swear!