However a SSM on the back of a small truck could be anywhere, making it a tad more difficult to find and eliminate. This is the basis of the USMC A2AD plan. They intend to insert small covert teams into various islands and resupply using small ships <4,000 ton displacement. The targeting info is received from off island assets, such as F-35, P-8A, HALE or MALE UAV etc. In an archipelago this could prove to be quite a good deterrent, closing off very large areas to enemy naval surface forces. This could work very well in both the Indonesian and Philippine archipelagos.
Personally, I think the USMC concept you describe is one of the least thought through concepts I've ever seen, and is the absolute last model I would want to follow.
First off, insert with what? A C-130 needs a runway, and is detectable by a number of sensors. A amphib is slow, and detectable by a number of sensors. The later is especially notable as the LAW's planned speed is 15 kt! How is that going to get around unnoticed? I cannot help but look at the IJN efforts with the Tokyo Express - most runs were identified (although not all were intercepted) with 1942 technology, the LAW will be half their speed and twice their size.
Now, when are the launchers being snuck ashore? Too early and you risk being cut-off or detected or irrelevant, too late and you can't sneak or are identified. With an ATG cruising at 20 - 25 kt and a SAG cruising at 30 - 32 kt, you have a small window. The further away your island is, the smaller this window gets. And the more pointless - if you expect a SAG through the Straits of Malacca and your nearest forces are Australia, do you sneak a AShM Tp ashore with a 15 kt amphib or do you just scramble a flight of F-35 or F/A-18E?
How long are these missiles going to be in location? Assume they can carry 7 DOS, what happens at Day 8? Noting the awesome speed of 15 kt, just how far is the LAW range from Darwin in 3 days? What is the resupply plan? What is the casualty plan? Remember, in SE Asia, non-battle casualties are likely to outnumber battle casualties, and are always present.
Now, what is the AShM Tp? Is it just a couple of launchers? Is it sensors? There are going to be some comms (which, by the way, blows stealth out the window). They are going to need some local security, probably a Coy or so. That's now 2x LAWs (with increased risk of detection) and 100-150 peeps dangling. There is also an increased signature, making them more susceptible to detection. The probably should be motorised at least, to enable moving from the beach, but that increases the logistic bill too. I know they talk about small teams, but a Coy is a small team for the USMC. It's also about the minimum you'd need - and remember that AShM are reasonably valuable elements of the force - they need that protection. Plus it'll be anti-ground and anti-air defence.
Taking the note that the targeting will be via other means, P-8 etc, every single one of those means is faster to react and better suited. Why spend hundreds of millions of AShM when you could by some additional missiles for the Super's or P-8s? If we go integral targeting, that's an emissions signature and a half - that'll get a response.
Now, what are the missiles? NSM is pretty easy, it's a Bushmaster sized vehicle. It'll be easy to move around a LAW and pretty easy to move around regional terrain. But, what if the missile is bigger? A Tomahawk ground launcher is longer than a HX-77 semi-trailer. That's going to be a dog to get around some places. The hypersonic fetish? Those missiles and trucks are even bigger. And just how stealthy am I in putting a Coy ashore with 2-4 massive semi-trailers?
Then there is extraction. Having fired 4 - 8 missiles (a paltry amount against any escort that has a couple of DDG or FFG) that's a pretty big signature. How are those forces getting out? A 15 kt ship?
Beyond that, where are these REDFOR ships sailing? Even the IJN stuck with reasonably known routes and didn't go through the small gaps - large chunks of their captured territory was just left alone. So, if you are REDFOR and you know where your convoys are operating, you can identify likely BLUEFOR AShM sites and pre-emptively supress them. There are not going to be many. Furthermore, anything that has a C-130-capable stretch of land is getting visited to prevent that happening.... The Tokyo Express happens because the IJN and USMC force a battle at Guadalcanal. There is a reason to be putting amphib forces ashore. If you don't need to be there, why would you go there?
The USMC concept is pretty flawed. It was held in high regard in AHQ in the late 10s until we started asking these questions. Frankly, I don't think is viable at all, for a small force like the ADF I suggest it's borderline criminal (if actually put into action and have deaths) or fraud (in peacetime).