I agree with the tiered approach to classifying conspiracy theories. I had a similar thought a while ago. But my reasoning was different: You could classify conspiracy theories on the basis of how much you are willing to believe.

For example, someone who requires rigorous evidence in order to believe something would only believe a very few things (eg: the most extreme being a mathematician within his field of study). On the bottom, you'd have people willing to believe things without a shred of evidence. Conspiracy theorists tend towards the latter - I don't mean that in a bad way. They tend to be intuitive, and their intuition fills the gaps where data is missing. If we all waited for rigorous evidence, we'd all be asleep concerning the NWO takeover attempt.