I think there is a flawed process going on right now. Australia needs air defenses for strategic defense, and it needs mobile systems to protect its troops once they are moving. I won't comment on strategic defense.
First, I believe the Skyranger is perhaps not a good option for Australia, in any variant.
Second, the solution needs to be a little more systematic than looking at a shopping list.
The following units need these capabilities:
Platoon - defeat perceptible small threats that can be affected by small arms fire. Perception aids need to be improved, for example by a BMS that might give general location to scan, thermals or AR to pinpoint it.
Kinetic capability needs to be augmented to increase likelihood of hitting the target. Systems like Smartshooter's SMASH, tested by the US Army, can enable one member per squad to apply accurate fire on a small, hardly visible drone.
Company - mobile small radars to augment detection, missiles like Stingers, to hit larger more distant drones, and to respond more quickly and precisely if any unit below company level encounters an urgent threat.
Battalion - defeat small MALE drones, helicopters, and some guided and unguided munitions.
Brigade - defeat cruise missiles, all forms of guided and unguided munitions, and some capability against manned or unmanned combat aircraft.
Division - defeat long range artillery rockets, short ranged ballistic missiles, all forms of aircraft.
No army in the world truly achieves all that. It takes an organic structure to supplement maneuvering forces to give them those capabilities. For example air forces that operate air defenses give their umbrella to divisions and brigades on maneuver.
But they still need those capabilities.
I'm not sure the NASAMS is a good option for any tier, because its missiles are almost prohibitively expensive against most aerial threats, and for any tier I don't see how it can defeat all the threat types unless it comes with a boosted version. But since I said no shopping lists, I'll focus on what Australia has in its inventory right now or has already financed.
The maneuvering forces are going to ride in either wheeled or tracked fighting vehicles, packed with medium caliber weapons, heavy machine guns, and ATGMs. Said weapons are augmented by APS which come equipped with radar and EO systems.
When you already have 30mm guns and ATGMs aided by radar and powerful EO, what really is the difference between the current weapon selection and the Skyranger or Biho?
Not much. Those products are made for those who need dedicated VSHORAD and do not have modern combat vehicles, or have some extra cash.
To make the current Lance turret more suitable to meet aerial threats on the same level as the Skyranger, you basically need to add only software changes, and allow switching ATGMs to MANPADS.
Of course some units, with vehicles of course, need to have a dedicated role of hunting aerial threats. That way you allow your troops to give some answer to an emerging threat. But just as much as aerial threats are evolving, so are ground based weapon systems - they become much more universal and capable of defeating a wider range of threats.
With available or soon to be available hardware, the Australian maneuvering units can meet any threat up to but not including MALE drones, and even defeat some unguided munitions. But to fulfill that they might need to make some serious changes on the networking level.
