It seems to me that although you present your arguments as arguments against the thesis (Z) that zombies are logically possible, they’re really arguments against the thesis (E) that consciousness plays no causal role. Of course thesis E, epiphenomenalism, is a much easier target. This would be a legitimate strategy if thesis Z entails thesis E, as you appear to assume, but this is incorrect.
If ‘consciousness’ plays a causal role, then we cannot imagine a world in which it is removed, yet everything behaves precisely as it did when it was present.
In that case, p-zombies are impossible, because the whole point of their hypothesized existence is that they’re identical in every way to people with ‘consciousness’ except that they lack it. If you remove a causal factor from people, they behave differently in some way, even if the difference is not immediately obvious to a limited observer. If the p-zombies really do behave precisely the same as they would with ‘consciousness’, and nothing else has been changed, then there is no difference between having consciousness and lacking it.
If ‘consciousness’ plays a causal role, then we cannot imagine a world in which it is removed, yet everything behaves precisely as it did when it was present.
In that case, p-zombies are impossible, because the whole point of their hypothesized existence is that they’re identical in every way to people with ‘consciousness’ except that they lack it. If you remove a causal factor from people, they behave differently in some way, even if the difference is not immediately obvious to a limited observer. If the p-zombies really do behave precisely the same as they would with ‘consciousness’, and nothing else has been changed, then there is no difference between having consciousness and lacking it.