AC could pick up a lot of YYZ passengers if they flew YVR-SYD nonstop. A connection in YVR is much more convenient than changing planes in LAX and dealing with US customs, and probably faster even though the distance is longer.
But right now, YYZ-LAX-SYD is faster and more convenient than YYZ-YVR-HNL-SYD. And you don't get your sleep interrupted flying through LAX.
What about range? What kind of load restrictions would AC need to fly any of their planes YVR-SYD?