Just as how Clash of Clans has spells Plunder Pirates should have potions. They would be produced in the Voodoo Hut and work by giving them to a certain troop ex gunners. The next battle all Gunners will have the ability that the potion provides. Thus in my opinion will bring a fun concept and make Voodoo Huts a better building in general.
Definitely need something else to spend the grog on. I've just started building level 9 walls, both academies upgraded, and besides troops I have nowt to spend my grog on. Potions would be a good option to have.