Oo, good point. On a side note I'm really, really looking forward to more news on that movie!
Back to Bond, it's all about the image I think. Certain characters are just so steeped in culture that the image matters. It's like how we all laugh at Nicholas Cage getting considered for Superman. It would be ridiculous! Why? We want to believe that's Superman, or that's Bond, we're seeing on screen. Certain characters have that image you need to uphold, and that's a testament to their popularity and timelessness.