Arrange 2 racks to divide the oven into thirds and heat the oven to 350ºF. Line 2 rimmed baking sheets with aluminum foil.
Arrange 1 (16-ounce) bag tortilla chips on the baking sheets in an even layer. Sprinkle 8 ounces shredded Mexican cheese blend (about 2 cups) evenly over the chips.
Drain 1 (16-ounce) jar pickles and finely chop (about 1 1/2 cups). Pat the pickles dry with paper towels and sprinkle over the nachos.
Drain 2 (about 15-ounce) can black or pinto beans, rinse, and pat dry with paper towels. Transfer to a medium bowl. Add 1 teaspoon garlic powder, 1 teaspoon ground cumin or taco seasoning, a pinch of cayenne pepper or red pepper flakes, and a pinch of kosher salt. Toss to combine and sprinkle over the pickles.
Finely dice 1 medium red onion (about 1 1/2 cups) and sprinkle over the beans. Trim the fat from 6 ounces cooked brisket, then shred or chop the meat into small, bite-sized pieces. Sprinkle over the onions and beans. Sprinkle the remaining 8 ounces cheese (about 2 cups) evenly over the top.
Bake until the cheese melts and starts to turn golden-brown, 8 to 10 minutes. Meanwhile, cut 1/4 medium lime into 2 wedges, and finely chop the leaves and tender stems of 1 bunch fresh cilantro until you have about 1/4 cup.
Sprinkle the cilantro over the nachos and squeeze a wedge of lime over each baking sheet. If you’d like, you can spoon guacamole, salsa, and sour cream directly onto the nachos, or just add spoonfuls to each bite as desired. Serve with hot sauce if desired.
