To make the banh mi veggies, add vinegar, sugar, and salt to a small saucepan. Cook over medium heat, stirring occasionally, just until the sugar and salt dissolve. Remove from the heat and allow to cool to room temperature. While the mixture is cooling, prep the veggies and add them to a large mason jar. Pour the warm vinegar mixture over the top. Screw on the lid and give the mixture a shake to coat all of the veggies with the vinegar mixture. Place in the refrigerator for at least 30 minutes, but preferably overnight. Drain the veggies before adding them to the pizza. The veggies will stay fresh in the fridge for 2 weeks.
To make the peanut dressing, add all of the ingredients to the bowl of a food processor or blender. Pulse until smooth. Season with salt and pepper to taste. Transfer to an airtight container and refrigerate until ready to use. The dressing will stay fresh in the fridge for 7-10 days.
Preheat the oven to 375 degrees F. Place the flatbread pieces on a baking sheet and top each piece with 1 cup of shredded Mozzarella cheese. Bake for 5 minutes. Remove from the oven and evenly top each flatbread with the cooked shrimp. Continue to bake until the cheese is melted and the shrimp are warmed through, about 5 minutes.
Top with sliced jalapenos, diced avocados, drained banh mi veggies, and fresh cilantro. Drizzle with peanut dressing. Slice and serve immediately.