What distances can control/comms links with these large UCAVs generally be maintained at, especially considering wartime conditions of EW and possible ASAT warfare resulting in loss of most or even all satellites? That's also an important factor determining whether it's feasible to conduct strikes against targets as far as Australia with them.
People are a bit too obsessed with going to Australia.
If the most valuable volume strike target remaining for China is Australia, the war is already long over.
Nearly all fighting will be on Korea, Taiwan, Japan and maybe Philippines but they're more of a punching bag. This is the grey zone where China holds some positions and US holds some positions.
There are tens of millions of target points in this whole region, and if China can match most of them, the war is always going to be unequivocally won.
Among many other products, US can't replenish semiconductors without access to either Korea, Japan or China itself. So even far before China has flattened every hostile city east of Taiwan province, US will already start running dry on crucial supplies.
Drones like CH-9 (or even better, the new hive drone) are perfect for that. They can operate in safe airspace and act as extra bomb trucks or even lob penetration aids and provide ISR to help other platforms get through with heavier munitions.
High end weapons are great for breaking up the US invasion force, but as long as there are countries that support US aggression, the US forces can simply resupply, rearm and/or wait around. Eventually, there may be issues with them bringing a huge numerical advantage (less likely now than a decade ago). To stop countries from supporting US aggression, a large low end ground attack capability is key.
Mass UAV and bomber attacks around the clock will cause severe loss of morale on the ground, making these countries in the 1st island chain withdraw support from the US, or at least unable to contribute to continued aggression. And once they're gone, Australia is just an open target.