Moderately on topic for the moment, I saw the stage production of Guards! Guards! at the Theatre Royal, Brighton. Paul Darrow (of Blake's 7 fame playing Avon - for us Brits old enough to remember) played the part of Vimes and his acting was about as wooden as the scenery
My friend, who had never heard of Terry pratchett, loved it tho.
Anyway, fully back on topic, I too was thinking of Mel Smith as Colon and possibly Andy Serkis as Nobby (playing the role of non-humans
so excellently should make the job of playing Nobby merely challenging rather than impossible). For Vetinari I reckon Patrick Stewart could make a great patrician with Ian McKellen as Lupine Wonse (or possibly the other way around, I just think Ian McKellen makes a good baddy
). For Vimes I was thinking of Dennis Waterman but I have to agree with Draywoman instead and opt for Philip Jackson and Pam Ferris.
As for Death, CGI is the only way to go with Christopher Lee's voiceover.
Looking back on my ramblings, it looks a bit like "What the cast of LotR did next".
I still can't figure out who I'd like to play Carrot or CMOT Dibbler tho.