I think you can look at the precedent that has been set with Venezuela and China to see who benefits from any trade thaw with Cuba.
Any company that is based in Cuba, will be owned by the Cuban government. Any US company will probably be under great stress to provide a lot of tax revenue to the Cuban government. Cuba is communist, and will stay that way. Even more so with additional US support. The Cuban ‘thaw’ will help keep the current government in place.
The main reason companies are in China, is for the opportunity to sell their goods to the 2 billion Chinese people. Even if only 1% are able to buy stuff, it's a lot of people and revenue. The other reason to do business in China is cheap labor and fewer regulations. Most manufacturing companies benefited quite a bit, as they were able to procure cheaper goods to sell.
In Venezuela, companies have found that their riches can quickly be taken away. It will be the same in Cuba. Venezuela will be the model for Cuba; Venezuela is Cuba’s number one trading partner and is most similar in the form of government. Canada will be the major country impacted to the negative since they are another large trading partner to Cuba.
Cuba has a small pool of people, (11 M) most in poverty, hardly worth setting up factories to sell internally, like in China. A manufacturing company would likely not sell many widgets to Cubans. Even if every Cuban could buy a widget, it would be a very small windfall. But the companies would be able to access the cheap labor, similar to a manufacturing company in Mexico, and supply the US. And if it was really going to be lucrative, some Canadian company would have already done it.
Cruise companies might benefit, as it would add another dimension to the ports. But it would not be a lot different than any of their other ports. It would be a novelty at first, not any better, just different. If it became a gambling paradise, or drugs and prostitution were legalized, it may be different. Perhaps an offshore banking haven would work, like the Cayman Islands, but it impacts few people locally. Cuba also has a lot of oil off shore, so drilling companies, or companies that supply drilling equipment, might benefit.
Cuba should have already been a mega paradise resort island, like Hawaii or back in the 50s. They should have been self-sufficient. They can grow food 12 months out of the year, but they need to import 80% of their food. They could have set up factories to supply their excess labor to the world, but they have failed in that regard.
So, I would look for the benefits of any US thaw to be to the Cuban Government. The Cuban government will be able to provide more to the people, at the expense of any businesses that set up there. And the Cuban people will see their government as their benefactors and they will be grateful to Castro family for the privilege of being able to eat.