Why not just remove the passport check in YYZ and YVR?

Then you get off your flight, and are let out in the international departure area. If you want to enter Canada or fly to the US, follow the signs. If you want to catch another flight, don't

Your approach sounds far too complicated, and only seems to be useful if the desire is to mix international and domestic passengers. But even there I see issues. International arriving passenger gives something to a domestic departing passenger. Now you've avoided customs.

I think LHR T2 is a better model (aside from the long walk), where all you have to do is clear security.