On the way to PVG, you can do LAX/SFO AS YVR BA LHR BA PVG and fly WT+ on the BA segments and earn AAdvantage miles on all segments. On the return you can do PVG BA LHR BA YVR on one day, but ythen ou have to overnight there before continuing on to LAX/SFO on AS. Prices (for WT+) are in the mid-$2500 range.