Place the chopped okra in a large mixing bowl. Cover with water and squeeze in lemon juice. Soak for 30 minutes and then drain the water. Rinse the okra under cool water and set aside.
Meanwhile, peel and slice the plantain, and place in a 1-quart saucepan. Cover with water, add salt and bring to a boil. Cook for 10 minutes until very soft. Remove from heat, drain the water, and cool. Add 2 tablespoons olive oil and mash with a potato masher until smooth. Set aside and allow to cool.
Heat 1/4 cup olive oil in a 2-quart saucepan, and add the onions and bell peppers. Sauté for 1 to 2 minutes, and then add the pork and shrimp, browning for another 5 to 7 minutes, until the pork is well cooked.
Using a blender, puree the chopped tomatoes, garlic and 2 cups water. Pour the puree into the saucepan, and add the vinegar, oregano and okra. Bring the stew to a simmer.
Divide the mashed plantain into 12 equal portions and roll into balls. Place the balls in the simmering quibombo stew, and cover. Simmer on low for 5 minutes, until the plantain balls have dissolved. Stir once or twice to distribute the ingredients evenly. Remove the sprig of oregano before serving. Serve hot with grilled or toasted bread.