You may remember him from... Goldeneye, Lord of the Rings, Outlaw
In our opinion, Bean's heavy face-wear during the first Lord of the Rings instalment didn't really suit him (we'd never say that to his face, though). Snake's messy growth should be a better fit.
Sean Bean is quite the hard man, with a voice tough enough to pop your eardrums at 20 paces. But his diction isn't quite gruff enough for Snake's spoutings.
We hope Bean would agree with us that his characters tend to be less talk, more action (see Outlaw). Our instincts tell us his no-nonsense Northern pragmatism would sneer at Snake's constant self-analysis.
Looks good in a cardboard box?
He's brutally effective as a soldier of any era, as shown by the Sharpe TV series and his stint in Bravo Two Zero. But Snake's emotionally detached sneaking seems too much out of character.