While I agree with your idea, I'm not sure if canonical is a fitting name. I understand the problem and already have thought about how to build a list that is not an off site link temple to find those high-rep-user-reference-answer answers more easily to link new questions there in case.
The problem I see is that people can easily add every crap (and adding new tags still has a too low rep limit/boundary) to their question and will surely mess up our list very quickly. And as WP is pretty large and we get lots of questions, this "queue"/list will quickly get a size where we really need to monitor the misuse a lot and need someone who adopts that tag as well.
Just my thoughts & concerns, not a definitive answer.