You can do (SW Pacific)-HKG-JFK and then continue eastbound (e.g. LAX-LHR-HKG); there is no restriction on a single flight number or even airline (other than affecting the segment count towards the 20 segment limit). But transiting NRT is often better for miles and just as nice in J (you can go MEL-NRT-DFW or even MIA). Lots of alternatives, each has something good and bad about it, all depends what you are optimizing.