So they will have a purpose in fighting with you, or atleast guarding? Well then ill think about a few ideas after dinner, and will come back later .)
Perhaps we, or you, should think about a persistent Pirate Village on another small island. Perhaps some sort of Hideout where they train those Dogs. Or even Parrots. Those Island could be kind of an Endgame PVE Content with lots of ressources, treasure, and Pirates.