He's been in the Senate even less time than Obama, right? I doubt that he would be an option.
Jim Webb will never do it. I don't think "politicking" is his thing.
He's not an option becuase he brings years and years of experience in the Senate. It's because he is a genuine war hero, was appointed to several positions involving the military during the Reagan administration, and called the Iraqi invasion one of the worst strategic blunders in modern history back in 2003.