Muffuletta Sandwich with Vegetarian Option

This is a delicious sandwich. I tried two versions using the vegetarian recipe, below - one true to this recipe, the other incorporating meats often used in muffuletta sandwiches (Italian mortadella and hot capicollo). The veggie sandwich turned out beautifully and, although the meat sandwich was good, it wasn't as good - I used less pesto and less tapenade in the meat sandwich and omitted the balsamic, which I think was my error. Anyway, I will try it again. I've included the meat as an option in the recipe, below. Essentially, there are loads of variations for this recipe, but the basic ingredient, as far as I can tell, that makes it a muffuletta is the olives - either tapenade or an olive salad etc.

1 small eggplant, cut lengthwise into 1⁄4" slices

2 small zucchini, cut lengthwise into 1⁄4" slices

1 large loaf ciabatta bread (recipe)

1⁄3 cup prepared pesto

1⁄3 cup prepared tapenade

2 jarred roasted red peppers, roughly diced (or more, don't be shy)

1⁄8 lb hot capicollo (optional)

1⁄8 lb Italian mortadella (optional)

1⁄4 lb mild provolone slices

2 Tbsps balsamic vinegar

1. Heat grill pan or grill to medium-high heat. Brush eggplant and zucchini with olive oil, and grill 3 to 4 minutes per side, or until charred and softened, dribbling more olive oil as needed. Transfer to plate.
2. Hollow the inside of the bread to make room for the filling. Spread pesto on one side of bread. Spread tapenade on other side of bread.
3. Layer eggplant, zucchini, roasted red peppers, meat (if using) and provolone on one side of bread. Drizzle with balsamic vinegar (warning, this will make the bread soggy). Season with salt and pepper.