Taking it as a given that any movie probably wouldn't work... if they did decide to make one or a series.
A female actor would probably work best for the Fool and Tilda Swinton sounds good but for a male actor I'll throw Cillian Murphy's hat into the ring.
Terran's mention of Donald Sutherland for Chade made me think that a young Kiefer (think lost boys) might have worked for Fitz. I always pictured Fitz as a bit short and if not stocky atleast broad shouldered but I cant remember if he actually was in the book or if it was just my take on it
.
I've never seen Seth Green in anything but comedies but I wonder if he could play Fitz, although again it really needs to be someone younger.
Joaquin Phoenix for Regal?