In any case, here are some additional actors (and possible roles for them)/list changes that I've come up with in the last few days:
Christoph Waltz - Quintus Cassius? 
Kyle MacLachlan - Victor Shadowman?
Julianna Guill - Lasciel/Andi (if her hair is dyed)
David Koechner - Carmichael  (Bruce Campbell is awesome {and a close second after Nathan Fillion for time-travel Dresden}, but as long as we're pointing out physicality/age-related problems with suggested lists, don't forget that Carmichael is fat and balding, and we'll have enough make-up budget problems already, w/o adding fat suits and bald caps/wigs.
Evil Bob should be the British one, BTW (and kind of a snob), so maybe Terrence Stamp?

I rather like these picks, I might just steal your MacLachlan pick for The Shadowman. I think however that Guill would make a better Andi than Lash/Lasciel(I've got Brit Morgan as my choice for Lash).

I personally believe that something like Carmichael being bald and fat isn't so important. To me, as long as Bruce Campbell is a little overweight and haggard looking then I feel like it's close enough. I'm looking for an actor I like that can be crass and jaded, as well as a bit of a slob, yet still be an excellent cop. I like Campbell because he can do all that as well as take a minor character that doesn't leave much of an impression in print and give him a much more memorable presence on screen. With an actor like Bruce Campbell I could see SPOILER!!! Carmichael's death in Fool Moon having a much larger emotional impact on viewers.

I agree that Samberg wouldn't work real well for Butters. On the other hand, I may have finally found a Billy.

For Butters I always picture David Krumholtz. He could pull off Butters' personality so easy it's scary.

I'm rather particular to Jim Caviezel for Marcone. He has the look and if you've ever seen Person of Interest you know he can pull off Marcone's character.