I could see John Hurt or Ian Mckellen as Kyril Sindermann.
They have that trained speaking voice, and he was described as very a compelling orator.
Though I'm a bit biased in that John Hurt could narrate anything and I'd be throughly sold.
And as much as I'm loathed to suggest he be in yet another bloody film, to me Karkasy could only really be Stephen Fry.