I would categorize my position as somewhere between 1 and 2, depending on what you mean by "conceiving". I think he has a name attached to some properties associated with p-zombies and a world in which they exist, but this doesn't mean a coherent model of such a world is possible, nor that he has one. That is, I believe that following out the necessary implications will eventually lead to contradiction. My evidence for this is quite weak, of course.

I can certainly talk about an even integer larger than two that is not expressible as the sum of two primes. But that doesn't mean it's logically possible. It might be, or it might not. Does a name without a full-fledged model count as conceiving, or not? Either way, it doesn't appear to be significant evidence for.