This poses an interesting question and I had to think on it before making a decision. I could see him as Jean easily. Too easily in fact. I think that he'd have made a great Grantaire though. In the book Graintaire is far from the pretty boy he is normally portrayed as [I'm looking at you Hadley (who admittedly does a good job.)] Also his in that moral gray area and Lon is great at moral gray areas. He could have made him sympathetic without making the character too much of a goody goody.

Yeah as I recall Grantaire would have looked more like Phrozo in the book. Lon would have been a subtle Grantaire, but only if it were in his early days definitely before Hunchback. Cuz as you know Grantaire isn't a leading role and Lon doesn't play second fiddle often, especially when a Valjean role (that is his character type) is leading. Though because of his role as Fagin I though he would be a good Thenardiers as well.

He would play Jean Valjean or Javert.I think that he would do a great job in both of these roles.