It isn't a viable solution for three fundamental reasons: persistence, economy, and mission.
Persistence.
Firstly, aircraft are not persistent. In a ground sense, it's why the ground elements of Army are essential - a combined arms team is the only force that can occupy the ground. If you don't occupy the ground you cede it to the threat for options. Aircraft cannot hold the ground, and you just have to look at the last weeks of Afghanistan when levels of airpower not seen since DESERT STORM were thrown at the Taliban - and nothing happened. At one stage every single serviceable AC-130 was operating...and they did nothing. And that's not a one off - look at the RAF/RAAF bombing of jungles in Malaya (achieved very little) and the multi-year campaign against North Vietnam (again, achieved little short of arguable LINEBACKER).
In the maritime environment it is subtly different (because you cannot hold ocean), but persistence is essential. Look at our own history with
Emden and
Kormoran and the impact their presence had on us. If you have a vessel, it's a threat all the time. The aircraft goes home after 2 hr. 6 h if it's a P-8. HMAS
Brisbane goes home after 4 weeks (assuming no RAS or maintenance). That's 4 weeks where I have to consider a threat if I am REDFOR; and unless it's Sydney Harbour or
maybe Port Moresby, let's not have any jokes about airpower maintaining a presence for 24/7 regardless of weather any further away. HMAS
Brisbane can do it
anywhere.
Economy.
We are a nation that requires imports. It sucks, but is understandable. Don't forget, the greatest industrial power on earth in 1914 required imports too. The only way those imports can come to us is via sea. The sheer quantity of oil alone can never be brought in by air, let alone the thousands of ISO containers that go through our ports each year. Australia's survival is tied to sea lanes. And in a time of war - who will protect the convoys/ships that sail them? Aircraft were vital to the Battle of the Atlantic in 1939-1945 yes; but it was the frigates, destroyers and corvettes that did the bulk of the work. Without them, Britain dies (see above about persistence). Australia is no different. Critically, those sea lanes start in the US or MEAO. What aircraft can reach that far?
Beyond that is the fact that Australian interests do not stop at the 12 nm line. Which means that we may have to put ground forces somewhere outside Australia again. In fact, that's almost a guarantee. So who protects the land forces going there? Who keeps their supply lines open? You cannot sustain a land force by air; you cannot move vital equipment by air in any meaningful numbers. The only option is by sea - and that requires escorts. There is a reason that GEN Leahy said the most important Army project in the 2000s was the AWD Project.
Mission.
Finally, we get to the mission. Unlike the other two services, the Navy has always had policing as a mission. We all have warfighting and diplomacy, but the Navy has the third one. To that end, how will aircraft take that on? How will aircraft tackle immigration, fishing, piracy or smuggling? No matter what your take is on individual topics, the RAN will be there aiding civil authorities. To say nothing of supporting one of the largest rescue zones in the world (~10% of the earth's surface is our responsibility!), and (because some of our neighbours simply don't have the capability), aiding other nations.
In addition, the diplomacy for the RAN is so much easier. Everytime they do a task, training, exercise or operational, they go somewhere foreign. The RAAF doesn't, the ARA doesn't. Even just moving from here to Japan to work in an exercises there will see opportunities to hit a dozen nations along the way. And when a warship rolls into a harbour, with a professional, well drilled and well dressed crew that sends a message - friend or possible foe alike. That Captain will have much more influence than an ARA or RAAF officer of equal rank would - just look throughout history where naval officers - especially RN - have been used as diplomats or helped shape national policy.
I'd highly suggest reading
SPC-A Commercial Publications: The Navy and National Security: The Peacetime Dimension | Royal Australian Navy to get a better understanding.
Final thoughts
I have a good mate who has come up through the minehunters. Their stories about getting to Japan are horrible - the constraints of weather and range that MFUs do not have to deal with as much have, at times, seen real risk taken by these crews that they shouldn't have to do. Doing anything to minimise the blue water capability of our Navy will undermine the ADF almost more than anything else. And yes, I have put my money where my mouth is and as an Army officer suggested halving the RAAF and ARA budgets to boost the RAN. With the exception of the air mobility arm (really just 36 Sqn for the RAAF) and nuclear weapons, air power is an enabling arm of war. They cannot achieve operational or strategic aims by themselves. The other two can, and do. And while Australia remains an island the RAN and ARA must remain balanced.