I had done some study on this subject a year and a half ago, with respect to South Korean LPHs. I don't think the existing Dokdoham class amphibious assault ships will be retrofitted for VSTOL use. The new 30,000 ton class is one ship. There are such limitations in range and payload on VSTOL aircraft, there is a question of their cost effectiveness.
http://civilizationdiscontents.blogspot.com/2018/08/posture-and-role-of-south-korean.html
https://thediplomat.com/2018/05/south-koreas-second-dokdo-class-assault-carrier-and-the-future-of-the-rokn/
In the crowded tactical environment in the immediate Northeast Asian region, i think one can question the desirability of such ships (VSTOL equipped carriers) at least for South Korea. I think they are useful in limited situations where national interests abroad need to be protected, and one needs to carry out an independent foreign policy or mission, not dependent on the commitment or policies of major state like the US. The situation in the Gulf of Oman right now is a good example where interests diverge. LPHs have a definite tactical role in the Korean peninsula region for amphibious assault.
The South Koreans are investing in a tanker aircraft fleet to extend the power projection capability of land based aircraft.
I saw a recently declassified document from 1972 that showed the US military mission in the Far East could play a tacit but important role in acting as a buffer or restraint on Japanese military superiority vis a vis South Korea. At the same time, the US is encouraging the arms race that is going on. South Korea may try to offset US pressure in the SMA military cost sharing negotiations, clearly a Trump directed policy that is not popular with our allies, by making further expensive US military acquisitions.
I have seen critical comments on the F-35c carrier based aircraft that tended to restrict tactical capabilities of the US large carriers in terms of effective combat radius and payload.
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