The "hard problem of consciousness" is masturbation because it doesn't help anyone to make any decisions. If you want to know whether P is conscious, just start with system Q isomorphic to yourself and change it by increments to match P. If it's behavior remains consistent at each increment then weak induction -> yes.

I guess the further stipulation is needed that P needs to remain predictable according to the same model as Q, as do all intermediate steps.

Sorry, replace "consistent" with "predictable".