Christian Bale is one of the most versatile actors in the business, and he'd need to only make slight adjustments to his widely-mocked Batman growl-voice to sound just like the husky witcher. Across most of Bale's great performances, he's consistently thrived most when playing the oddball or outsider. From American Psycho to American Hustle, by way of Batman, he's always made a great maverick, who functions by his own code rather than that set by social norms. Physically, Bale's proven himself to be the most malleable guy in the business - so the filmmakers just need to tell him to get trim, muscular and scarred like Geralt and he'll happily go away and do it - complete with authentic sword-scarring.