Would you not be best doing a CPH-SIN-MEL redemption with a stopover in SIN for $100? And sorting out SIN-HKT separately - either point or paid?
Below are my options as I see it (this is as much for me to breakdown to make a decision!), happy for anyone to pick holes or suggest a better idea.
Option 1 as suggested:
CPH-SIN-MEL = 105,000 SQ Miles = 141,750 VA Points
Taxes approx $65 + $130 stopover fee = $200 = $400 total
Infant cost estimated $600
Side Trip SIN-HKT-SIN = $300-$400 for 2 adults and 1 infant in economy
Total cost (2A 1I) = 283,500 points + $1400
Option 2:
CPH-SIN-HKT = 92,000 VA Points
Taxes approx $80 = $160 total
Infant cost zero
HKT-SIN-MEL = 65,000 VA Points
Taxes approx $80 = $160 total
Infant cost zero
Total cost (2A 1I) = 314,000 points + $320
Points difference = 30,500
Dollars difference = -$1100
Cents per point = 3.6 cents which seems pretty good.
So the question is 30,500 points worth $1100? And it then means no separate tickets and all of it in business class instead of the side trip being in economy.