In terms of fragmentation, I don't think this will be done on the Australian end, but rather, on the overseas end.
As below, IMO, QF should consider CPT, SEA and somewhere else in South America with an LA hub, like EZE.
The problem with JNB is that South Africa looks to be headed for economic stagnation, especially with the new government's policies there. That may affect business traffic, particularly to JNB. That being said, a permanently weaker currency makes it more attractive to holiday in, so SYD - CPT or PER - CPT could be an option (like with CX headed there).
The problem with YVR is that AC has already taken that market, adding both BNE and MEL to their network; I'm not sure that Australia - YVR could support more QF routes. In contrast, QF could tap that region through a SYD - SEA service. This would connect to the AS SEA hub, and tap wealthy SEA tech traffic. Many, like CX and EI, are launching SEA.
The Aussie dollar is heading below 70 US cents, and may even get to 65 US cents. If that happens, I don't see much QF Group expansion to HNL for a few years, at least. In this period, HA will likely be able to start MEL, relying on its HNL hub to tap mainland traffic - QF doesn't have a HNL hub, so relies on O&D. They could replace JQ metal with QF's, though?
The problem with SCL is that it is already dominated by LA, who fly to AKL and MEL, in addition to SYD. I'd let LA take SCL, with QF to consider Brazil (as the main prize), but potentially down the road EZE or LIM (as LA has hubs there) too. AR is considering a return to SYD - EZE, so maybe QF could beat AR to it. This would put pressure on competitor NZ, too.