Perhaps I can have just a quick response to that.
You've put your finger on absolutely the best constitutional hope for legislation to survive, and everything you said was correct, but despite that being the high-water mark of constitutionality, it's still pretty low because of how few cases have been decided under POGG and the fact that you do currently have nine out of 10 provinces co-operating to bring down drug prices. The only province that isn't co-operating isn't there because it doesn't want to be. That's Quebec.
While provincial inability isn't a hard test, it's a consideration, as Professor Ryder said. He's exactly right. That consideration is not on your side.