Adjust the oven rack to the middle position in the oven cavity. preheat oven to 350ºF (177ºC).
In a large mixing bowl, or a 4-cup glass measuring cup, whisk together BBQ sauce (1/2 cup), ketchup (1/2 cup), water (1/2 cup), brown sugar (2 tablespoons), creole mustard (2 tablespoons), vinegar (2 tablespoons), liquid smoke (1 teaspoon), garlic powder (1 teaspoon), and cajun seasoning (1/2 teaspoon); set aside.
Set 6 slices of bacon aside for topping the beans later. Chopped the remaining bacon. In a 12-inch nonstick skillet, cook the chopped bacon, until crispy. Remove cooked bacon with a slotted spoon to an extra-large mixing bowl. Drain the bacon grease and save for another use or discard.
In the same skillet cook and crumble breakfast sausage (1 pound) into small pieces, over medium-high heat. Cook until fat begins to render from sausage, about 5 minutes (it won't be completely cooked at this point). Add onions and cook until sausage and onions are well browned, about 15 minutes. Remove and discard excess grease.
Transfer cooked sausage/onion mixture to the extra large mixing bowl.
Add baked beans (3 cans), pinto beans (3 cans), RO*TEL (1 can), BBQ sauce, and crispy bacon pieces to the extra-large bowl.
Transfer bean mixture to an extra deep 9X13-inch baking dish (Do Not use a standard 13X19. The volume of the beans is too great for a standard 9X13-inch standard pyrex or ceramic baking dish). You can also use a metal 9X13 dish, or split the beans up in 2 pans. Place the baking dish on the rimmed baking sheet.
Cut the remaining 6 slices of bacon into 1-inch pieces and decoratively arrange pieces in a single layer over top of the beans.
Bake for about 1 1/2 hours, or until beans are bubbling and bacon is rendered. Let cool for 15 minutes. Serve.