>Planning a RTW starting in Vancouver,
>with the first leg being YVR-NRT-PVG.
You could also look at originating in Seattle. Sometimes on Air Canada SEA (-> YVR) -> NRT is cheaper than YVR -> NRT. You likely still won't be able to interline, but might find some options with a longer layover.
Cheers,
Geoff Glave
Vancouver, Canada