Yoinking across to a more general discussion....
The RAN may currently carry more non-warlike, diplomatic and constabulary tasks but it could be asked, should they? We have ABF.
Currently to the nature of Operation Sovereign Borders naturally the RAN has a large role to play. But the RAAF plays an equally demanding role.
I do think for now RAN needs to maintain responsibility for patrol and control of current and future assets but one day this may need to change.
Not only should they, but they always will. Even with the biggest, baddest ABF you can think of plus a full strength and capable Coast Guard, it'll be the RAN which has the ability to operate into the Southern Ocean to rescue sailors or capture fisherman. Or chase a fishing vessel 3/4 of the way to South America. It is inherent to a Navy, the things they need for war (equipment, thinking and processes) means they will always have diplomatic and constabulary tasks. And, while the other two will help, the RAN will always carry more...
I think you might be understating the non-warlike tasks of the other services. Peacetime engagements such as overseas training and capacity building, humanitarian and disaster relief (at home and abroad), and cooperative activities with other agencies are generally the role of the Army. But in line with the join forces concept, they generally (especially OS) need the Navy or Air Force to get there. Service rivalry aside we need to be a joint force. We do not want to head down the US path of services competing for funds. This has led to some colossal economic blunders and runs the danger of the military influencing politics, a slippery slope for a liberal democracy.
Not at all. The Army has spent more time doing non-warlike tasks than warlike - even if at least one of those non-warlike tasks saw my helicopters getting shot at. But in discussing the wider range of tasks the RAN carries, it's not service rivalry or the like.
The work we do in the region is essential. Our Sect - Coy sized exchanges and the like are a cornerstone of our defence in building regional relations. And they pay back, as anyone who has seen the deployment of forces to Australia post-disaster in the last couple of years. But, for constabulary tasks these nations generally have their own forces and we have the AFP, and for diplomatic tasks it's very low level. For starters, the biggest Army force we regularly send overseas will have, at most, an O4 in charge. Perfectly fine, very little influence. Normally the ranks are lower. A ship will have at least on O5. There is a subtle, but distinct difference - even within our own nation.
I'm not arguing against a Joint Force. The fact I, as an Army officer, argues for the RAN should indicate it's a very good idea that has inculcated itself within the ADF. But a joint force demands an honest assessment and understanding of roles, including areas one's own service doesn't do well at.
Port visits are great for as a token diplomacy. But an overseas Army presence in the country is deeply engaged politically, and usually are more closely involved with local populations over long periods in a way in which sailors and air personnel are generally not. This sends signals to the host nation, other states and non-state actors. A highly visible and clearly understood presence. This gives a high level of reassurance and offers a level of diplomatic commitment that a ship stationed offshore, simply cannot. The same could be said for disaster relief and Army operations in Australia, the presence of Army personnel rallies, engages and reassures the community in a way that other agencies cannot. During national emergencies its usually (but not always) Army helicopters that typically called to assist. That said, I am sure the sight of Navy ships during the black summer 2019 fires was a sigh of relief to the people of Mallacoota.
A carrier or ship 100 kms off the coast sends a powerful signal to an adversary and to the nation you are supporting, but it is a mixed signal. To the adversary there is significant firepower sitting off our coast, but they don’t care enough to get up close and personal and risk standing between us and our objective. To the nation you are supporting it is yes, we will support you, but not stand shoulder to shoulder with you and face the threat in the mud, suffering in the same way you do.
There is a mix of concepts here, but some are correct and some not.
Generally speaking, in times of peace, Land and Air forces (the latter especially) are not seen by the wider population, much. Their area of influence is much smaller. Look at Pitch Black for instance - lots of 'stuff' for Darwin and Tindal populations, very little (including media) down south. Often such forces rarely leave the base; in my first overseas, non-deployment, trip we spent all our time on the base - we never went outside the wire. A ship visit on the other hand; it gets more media and has a wider impact. If USS Carney were to rock up to Darwin on her way home, the media will be more. This will be increased if she visits Perth or Sydney. And when she does, she'll drop 280-odd people into a CBD - because that's where the ports generally are. That's a Bn or Wg effort. If she comes with another ship those numbers increase. At the pinnacle, Perth, Brisbane, Darwin, and Sydney residents still speak of times when USN carriers have visited...
But even taking the smallest ship, they have outstanding impacts. A mate was the 2IC of one of the MHC to visit Japan. Their trip up and back hit 19 ports, something like 8-10 countries. They worked closely with various DFAT staffs across this, entertained senior foreign personnel on board - all providing a smart, approachable, clear statement of Australian respect and friendship. Sure, the PO's had some work to do the morning they left each port....
When you are attempting deterrence, your thoughts are more on track. The ultimate level of support to a friend is parking a Armoured Bde(+) by their side. Air forces, especially, are simply too movable - there's no guarantee they won't fly away. But you can't do that with heavy units.
RAND found this when looking at forward deployed US forces. Which is why, when our 'strategic experts' talk about no role for armour in the region, I think they underestimate the statement that 1 (Armd) Bde (or 3 (Armd) Bde now, I suppose *sigh*) being deployed to, say, Vietnam does. It might not deter, but it'll cause a rethink at least.
Ultimately, it comes back to what are you trying to diplomatically achieve. The ADF is simply another toolbox that DFAT and the Government of the Day has, but like every tool box the contents are varied, and some do better than others.