
To make the Italian dressing: In a jar with a tight-fitting lid, combine the olive oil, vinegar, parmesan, garlic, oregano, salt, and pepper. Shake well to combine.
To make the sandwich: Place the loaf of bread on a cutting board, perpendicular to you. With a serrated knife, cut lengthwise through the center of the loaf, almost all the way through the bread. You should be able to open the loaf like a book.
Hollow out about 1 inch of the inside of the bread, from the top and bottom of the loaf, leaving a 1/2-inch border around the edges.
Spread the mayonnaise on the cut side of the bottom half of the loaf. Arrange the salami slices in an even layer, folding or shingling slices as needed. Repeat with the pepperoni, capicola (or ham), mortadella (or bologna), and provolone.
Top with the shredded lettuce, tomato, red onion, olives, and banana peppers. Drizzle about half of the dressing all over the veggies on the sandwich (save the remainder to serve on the side). Carefully fold the top part of the bread over the top of the veggies.
Place 8 (6-inch) skewers about 1 1/2 inches apart in the sandwich. Using a serrated knife, slice in between the skewers to portion. Serve immediately.