He'd feature somewhere. Obviously Benedict Cumberbatch would play DPR - he'll shift shapes, it's his type of role.
After seeing what DPR looks like, someone like Emile Hirsch would be more appropriate I think.
Benedict Cummberbund is too old. Hirsh could work.
http://www.coindesk.com/5-actors-play-ross-ulbricht-silk-road-movie/Robert Pattison could too looking at that picture.
It's not about how one looks, BC has started something of a habit of playing real people lol. BC for the win.
On a serious note though, Emile Hirsch definitely looks the part.
You've got to look a little bit like the person you're meant to be playing. I've not really seen Cumberbatch in much. Only a few of his small parts.