For anyone wondering, I was able to find a wonderful agent who was able to actually split the Island Hopper into six independent segments, allowing me to choose different seats for each leg (and Economy Plus only for MAJ-HNL at a reduced price) and earn miles for each separate leg. So this is actually possible for someone willing to do it (the last agent I spoke to was 100% positive that this was impossible due to "too many legs for the ticket").
For HKG-PEK, I ended up booking an award flight on BR/CA with one night layover in TPE
That, and my positionning flights from YUL to LAX means I now have 18 legs for this trip. Should be quite an adventure!