Im suggesting the plugin 'SuperiorSkyblock2' to be added. As the other skyblock plugins aren't nearly as good/customizable as this one. This plugin consists of upgrading, promoting members, changing permissions of each island rank, custom island builds and a lot more.
https://www.spigotmc.org/resources/️-superiorskyblock2-️-the-best-core-on-market-️-1-16-support.87411/