In to YUL; out to GCM; in to YYZ - there is no restriction on multiple stopovers at the same place, so if it is more convenient you can return to YUL rather than YYZ

YYZ-LAX-MEL – you don’t say if you want to stopover in LAX – but assuming you don’t care too much and that you’re after plenty of good premium cabin time – perhaps consider YYZ-xHKG-SYD, which will be CX’s great premium cabin and then either CX again or QF’s A380 on the HKG-SYD leg

Visiting Australia in January (which is when the open is on) – good time of year for SYD and MEL, but maybe not so good for BNE and CNS; rainy season, chance of cyclones, I'm no scuba diver so cannot comment on that aspect. Perhaps consider later in the year when the weather is better in the North and, compared to YOW, the weather in the South is very mild (I’ve been in YYZ & YQT in Feb – SYD/MEL in Jul/Aug is nothing like that!)

Remember – you have 12 months from the date of the first flight; so if you spread it out more, would you have more vacation time?

If you did decide to spread it out, then my thoughts are:

• Drop the intra-Australian flights – QF’s domestic J product is nothing special, the flights aren't long, and economy fares are reasonably priced so purchase them separately
• Use the segments freed up to have a few more Nth American side trips over the winter. In this regard, there are plenty of direct flights out of JFK to various warm spots, so consider KRT-AMM-JFK-(up to 6 segments, i.e. 3 return trips)-JFK-xHKG/LAX-SYD/MEL/BNE, or JFK-SYD direct (but that’s a B747 not an A380)
• Maybe have a second stopover in the Middle East/Europe at the start, for instance KRT-AMM-MAD-JFK… or KRT-AMM-MCT-AMM-JFK…
• Maybe extend the Asian leg - between Australia and CMB, you could look at adding NRT/SIN/BKK…