I wonder if the SYD-SFO-YVR flight might be able to keep transit pax from going through immigration because it is a same plane international flight? I think NZ does this on the AKL-LHR flights through SFO & LAX...
That way you could do SYD-SFO-YVR-LHR-(Europe)-LHR-SIN/BKK/HKG/JNB/etc.-SYD at least.