Factotum was pretty crappy. I don't like Matt Dillon as it is. And he was about as effective in that role as a one legged man is in an ass kicking contest.
In most circumstances I'd agree with you and while the finished product may end up off the mark. I'm hoping he pulls it off. It looks like that he's only directing, not acting. Also the kid playing 12 year old Buk is ugly enough to be believable.