I cant help but imagine a Hyuga or 22DDH fitted with a bow ski jump and roos painted on the funnels rather than a modified JC1. I know its not going to happen but as we already have the LHDs why not go for something to dramatically increase the RANs ASW capability that can also operate F-35Bs and even a helibourne MCM capability.
Modifying a LHD to carrier would be pretty extensive. While not a ship designer (and I know there people who are on here), doubling the power plant, ensuring hull works at 30kt, increasing fuel bunkerage by 1000 or 2000t are no small modifications. Then you have generally a not very optimal hanger space that you have live with. Lots of modification, lots of risk. While the Japanese and Koreans are certainly capable, they haven't had proven carrier experience. I would love to see what they could put together.
Cavour however is in the water now. Designed by a country that has carrier experience for decades, Spain too has extensive operational carrier experience. Cavour (or a Cavour+ with a 10m plug) would offer IOC, as you could put 100 sailors and aviators on one today to start training. While Spain wouldn't have a ready to go inservice carrier design, they do have a carrier and extensive carrier design experience and we have established a joint build program with them. Spain will build a carrier, so upgrades and training can be shared.
Cavour with a 10m plug would allow greater endurance and range.
If Australia ever went down a carrier route, it would all be about quick IOC and lowest risk. Meaning someone with a carrier, with extensive carrier design experience. Even then, things can go wrong (France and CDG for example).
IMO the best would be the UK. Lowest risk, most experience, most carriers, easiest fit. Although I don't know how the RAAF would feel basing its entire fast air on a ship.
If we could get the money together for a 3rd LHD, then the cost difference between a 3rd LHD and a light carrier is fairly small. Cavour type ship has fairly extensive amphib capabilities so could act as an amphib particularly if deployed with a LHD or a Choules. The carrier would focus on air deployment while the LHD could use its dock to focus on sea deployment. Cavour has done humanitarian duties in Haiti so its not theoretical capability.
We need a 3rd ship to provide amphib capabilities to meet the original goal for an amphibious landing. With the US seriously cutting back capability and forces, the additional amphibious and protection a carrier would provide it would seem to be sensible to look at this once the first LHD is operational. But then again we may get another civilian Skanky Burger ship to provide all our amphibious needs with 1 roof mounted helipad.