The explosion of kosher traveling isn't that old. So I disagree with this.
Though I doubt a place like this is sustainable in the middle of no where open all year long and 100% kosher.
A kosher option would be easier to sustain.
A long time ago, before Cancun was built, when Acapulco Mexico was the place to go on vacation. They had a lot of Jewish tourists as well, to the extend that one of the hotels there would become a kosher hotel for part of the summer each year, complete with a shul and everything.
Maybe a similar model can work, where there are kosher months and non-kosher months?