Thanks for advices. Considering these, i have yet again made changes as follows:

syd-hkg,hkg-yyz,yyz-ord,ord-sju,sju-pos,pos-mia,mia-bos,bos-sfo,sfo-jfk,jfk-dub,dub-mad,mad-cai,cai-lhr,lhr-hel,hel-sin,sin-bkk,bkk-bom,bom-hkg,hkg-akl,akl-cns,cns-syd

Outward flt via HKG should be stopover only of <24hrs.
In all there are 21 sectors but i would surface YYZ-ORD to cut out one sector in USA (from 7 to 6) and thereby reducing overall to 20.

BOM is important but with HEL-SIN, I gain with over 5000 threshhold. I can take AY to BKK and CX to BOM.

Overall, ORD and BOM are important. I do want to go to POS just for cultural reasons.

Thanks again. Guidance is much appreciated.