I guess I am not a big Whedon fan. Not saying I have anything against it, I just never really got into any of his stuff. I watched maybe 30 of the 144 episodes of BtVS. I never watched Firefly, and I saw maybe one or two episodes of both Angel and Dollhouse. It's not that I didn't like them, just never got into them.
With that said. I would not like to see a Dresden Movie cast with the frequent Whedon actors. Not to mention that we are comparing a TV show cast to a Movie Cast. Granted most these actors have faired well on the silver screen, I would like to see a new mix of characters that can't really be associated with a group of unrelated characters.
I am glad that a couple people actually like my Kristen Bell pick for Murphy though even I admit she seems just slightly young. But I admit SMG would be a good choice too.
I don't see Charisma as Lara at all. I kind of have
Famke Janssen pegged here. Or maybe
Kate Beckinsale though that choice would obviously be heavily influenced by her role in Underworld.
I like Eliza Dushku, she isn't quite how I pictured Elaine, but it could work, IMO it depends on who plays Harry, and the chemistry between the two actors.
Alyson Hannigan.....YES! I have always been a fan, American Pie though, not really because of BtVS. Something about her really strikes me, but Ally is married to Alexis Denisof, this really would turn into a Whedonverse reunion.