I'm only a novice in these discussions.
However, why is everyone only just discussing the A2/D2 of the JSM in this context with it's range?
We are acquiring 200 x maritime LRASM. I wouldn't have thought it would be too much of an extension to acquire the land based block. LRASM-SL, which can be fired from HIMARS (first tested as far back as 2017 by USMC)
In terms of your post specifically, the US Army first lifted a modified HIMARS with a Chinook (also in 2017), even carrying a LRASM, you are looking at ~8,000kg vs the Chinooks nominated 24,000 pounds (10,886 kg) lifting capacity. No reason they couldn't be transported into remote island choke points off of a LHD.
It's certainly a different discussion with a big increase in range from a island choke point vs a JSM.
A HIMAR located on Christmas Island fitted with LRASM-SL has a deterrent range to within approx 450km of the Spratley Islands.
Umm... Not really.
If (big IF) the ADF were to acquire any one or more of the longer-ranged, there would still be all of the issues involved in actually getting whatever launching systems used landed and into position, as well as landing the associated personnel and whatever escorting/security force, and then establishing and maintaining the logistical train required to support the landed force.
As for the greatly increased deterrent range, IMO that would not really be an effective increase. Whilst the missiles used might have considerably longer range, there would still need to be sensing systems in place to detect and ID potential tracks, and given a greatly increased range, such sensing systems would need to be able to track and provide updated targeting information if/when targets move. For some of the more extreme-ranged shots suggested, missile flight times could be in the realm of 1hr, which could see a target having transited several n miles. If the ADF were to acquire a land-based AShM capability able to reach the Spratly Islands (even from much closer islands) Australia would still need to have some sort of system to detect, ID and then target vessels in and around the Spratly Islands. No sensor system, no ability to 'see' targets, much less shoot at them.
As for using CH-47 Chinooks to airlift AShM and launch units to distant islands from
Canberra-class LHD's, that could be done, sort of... The combat radius of a CH-47 is ~200 miles, which is still fairly close given the relative distances involved in the Pacific and surrounding seas. Keep in mind though that any deployed AShM, launchers and personnel will also need to be landed as well as supplies. Also, I have significant doubts that a regular M-142 HIMARS could be lifted by a Chinook, since
this US Army page on the HIMARS indicates and empty weight of 29,800 lbs which is ~6,000 lbs over the lift weight of a Chinook.
In short, Australia would still encounter issues getting the missiles and launchers to area where they could operate. Issues relating to logistics would also still remain since everything would be deployed some distance from mainland Australia, and Australia would need to be able to get resupply to the area. Lastly, there would still be the issue of being able to detect and ID targets from a distance.