I liked the cast they had for the Dresden Files TV series.  Just drop the tv series continuity and start over with a theatrical version of Storm Front and switch the actresses who played Susan and Karyn back to their originally intended roles.  (They were switched in the series due to there being a a real Karen Murphy on the Chicago PD.)

I think Paul Blackthorne did a good job and when I read the books, I picture Harry looking just like him. 

Add Orlando Bloom as Thomas.