So for Bill's "qualifying" accords or what have you, he does have a Bachelors of Science in Mechanical Engineering, which applies engineering, physics, and material science (which deals heavily in regards to molecular sciences and properties of physical objects), and is a scientific discipline that overlaps frequently with astrophysics and meteorology - namely in regards to space craft. As he's used and applied his degree and knowledge to several applicable projects (namely on space and air craft), I would say that certainly qualifies him as "a scientist". Just not a biologist, or a geologist.
However in the debate, and now his tour of the ark, he never gives the reason of "Well, because I'm a scientist". He always said that he knows what he's presenting because he's seen the evidence himself. He's been shown the process, or he's actually looked at geological levels. I find it a dangerously silly suggestion (and almost dogmatic) that if he's not "a scientist" of a specific discipline that he doesn't know what he's talking about. That "scientist" becomes an exclusive term.
But more than this, he is a science educator. Which is largely what he does in these debates. With the time constraints given to him in the debate, and surrounded by pushy people in the Ark (no matter how professional you are, that is intimidating), he explained the processes of radiometric dating, the observable history of geologic deposits, why 45,000,000 year old volcanic rock would surround 4,000 year old petrified trees, how we tell how old trees are, etc. Things that any of us could do, really. And if he's "not a scientist", it's still viable and true.
Given what Bill knows, and given his contributions to the scientific community, I think he's more than qualified to present scientific method, theory, and evidence to people in a way that's easy to understand. Just because his degree is in Mechanical Engineering (which, it's still a science degree), doesn't mean that he doesn't understand geology, meteorology, physics, etc, and can't present them to people as an educator.
