I think you really have to look at the Jones Act and the PVSA slightly differently. The Jones Act is shipping, and continues the impacts of imperialism on places like Puerto Rico and Hawaii, around essential goods. The current argument du jour for maintaining the rule is around CBP and Homeland Security.
The PVSA was also originally about coastal security - in 1886, it was in line with global precedents restricting trade along a country's coasts for economic and defense purposes. The law did not address vacation cruising as that market didn't really exist. Even luxury cruises were about transport - you couldn't do a European tour without getting over the ocean.
They have done an exception to the American-built element in the past for the PVSA. In 2004, Norwegian was granted an exemption for three ships (none of which were entirely built in the U.S.) to operate solely within the waters of the Hawaiian Islands without the need to call at a foreign port. I believe one is still in service.
The most likely exemption to the PVSA is that exemption - the ship build origin. The likelihood of waiving tax rules and labor law are really low. Under international law, ships are subject to the laws of the country where they are registered. There were a host of proposed exceptions in the 1990s that went nowhere, and a 2001 bill was proposed to allow U.S.-owned foreign-built cruise vessels to enter the domestic market for a limited time if the operators agreed to build replacement vessels in the United States. Also went poof. The lines have traditionally wanted all or nothing - let them sail foreign flagged ships under foreign labor laws between any two ports. And that has not helped their position for waivers or help.