I see your point, and it's valid.
Another question: Are your understanding of the character based on the game or the books?
A corollary: Is there a difference between Geralt of the books and Geralt of the games?
pibbur who doesn't know.
I've only read part of Last Wish - so I've yet to establish the potential differences.
I would assume the characters themselves are reasonably similar - with certain concessions made for the very different mediums.
But then again, I'm almost never a purist in that way. Only when it comes to Star Trek and Tolkien
I'm not "married" to anything in Witcher - so I'll likely be quite accomodating when it comes to certain changes.
However, I think it's pretty clear what Geralt is like if we take his physical characteristics and the "core" of his personality and what it means to be a Witcher (the consequences of mutations, etc.).
Which is exactly what you would need to take into account when casting such a role.
For instance, the reason I don't think Caviezel would be a great choice - is that I know a few things about him as a person. First of all, he's deeply, deeply religious - and he's also extremely dedicated to supporting his faith - much more so than I would think his career in popular entertainment. Playing Geralt would seem to be a very strange choice - in that case.
Beyond that, I think he's too soft a person in terms of his outward appearance.
For him to change into Geralt would take a very serious transformation of character - or maybe I'm not giving him enough credit.
Why? Because he's driven from a place of emotionally rigid principles. I don't think such a position is a great place to start for a role that's essentially void of emotion - at least on the surface.
In that same way, I think he would be a terrible person to play Sherlock Holmes or a Vulcan in Star Trek - because they share the same core characteristics of Geralt.
However, there are certain very notable exceptions.
For instance, if you look at Sofia Helin (the woman who plays Saga Noren in "Broen" - which is a character with pronounced Asperger - and which is infamous for her lack of concern or understanding of social graces) - she was actually the perfect person to play that role, because she's EXTREMELY sensitive and emotional in real life - and that comes through in Saga in a very, very profound way.
So, it can work - but, again, I don't think it's the norm.
For someone like Mikkelsen, it would be a trivial task. Not only does he have a much wider range - he's also not bound by outside factors that really have no place in the life of an actor taking his craft seriously. Beyond that, he fits the look almost to a tee - and he's also a little exotic looking, which will only aid the part - I think.
But that would be my perception.