I read a very interesting article attempting to destabalise physicalism entiorely. I'll try and find out what it was called, I think it was wriiten by a professor and a Doctor from UCL, it was very good, ending in something like, this should be the last ever article on physicalism, but we doubt it. Very persuasive, but I couldn't help feeling some sleight of hand was going on somewhere.
The general gist of the argument, which doesn't follow most of Chalmers' work was, physicalism is an attempt to explain the world, psychology is not termed a physical science, the reducability of the physical sciences to pure physics is an unattainable sham , thus psychology is no less a science than physics/chemistry/biology, thus it is impossible to reduce the world to the physical.
However the particular claims you made above was that it was not nomologically impossible to have consciousness without the physical. I think that is wholly dependant on one's interpretation of the meaning of conciousness. Without any sort of input from the physical world, what would consciousness mean? I can't imagine such a thing, I personally don't think it is even logically possible, let alone nomologically possible. What is consciousness without stimuli? There must be some sort of input, ultimately from a low (physical) source such as perception to be able to form consciousness. If you get rid of the physical in brackets there youmayjust be able to make it logicvally possible, but certainly not nomologically as I see the world today. That just leaves you at a skeptical position.
once all of the relevant neural structures and functions are explained, how does this automatically necessitate the existence of consciousness?
That's the job of the neuroscientist. Conciousness couyld purely be form, the structure of the system. i think it was lebeinez who said conscioussness would always be outside our grasp of explanation. I suppose it depends on whether you believe a computer could attain consciousness.
I do realise, of course, that structure seems a poor way to explain the phenomenal consciousness of red, blue, tea, the elation of discovery or the pain of a gunshot wound. But just because the structure may be complex, it doesn't mean it is inexpicable, though words may do it little justice, after all we talking hundreds of thousands of years of progressive design here. Any attempt to say that consciousness is something more beyond the physical must alwaysrest on the dualist's shaky mind/body bridge.
There are good and bad points about both the view that you hold and the view that I do,that much I admit
 I think, not having read all his work as I said in an earlier post.
 This was the long and fairly technical part of the article which needs a lot more arguments to back it up, but I can't remember it in it's entirity nor do it justice. Though this was the particular place where I thought the sleight of hand was going on.
 I refer to evolution of course. Though I do side with the Dawkins and others when they say that it's not always beneficial, and in fact can be seen as 'evil' at times. Progressive is perhaps the wrong word, but it is the most appropiate I can think of.