To make the pickles, combine the rice wine vinegar, warm water, 4 TBS sugar and kosher salt in a large bowl and stir to combine and dissolve the sugar. Use a julienne peeler to grate the carrots and daikon into thin strips, then place the carrot and daikon into the pickle brine. Add the sliced jalapeno. Cover and refrigerate pickles for at least 8 hours – pickles will improve with time and will last in the fridge for a few weeks.
To make the pork belly, cut the roasted and chilled pork belly into 1 inch cubes and set aside. Heat the canola oil in a saucepan over medium heat, then add the garlic and saute until fragrant, about 60 seconds. Add the fish sauce, tamarind paste, Thai chile, and peppercorns and cook for 1 minute, then add the pork belly to the mixture. Stir the pork belly to coat with the sauce, and cook until the pork belly is very hot and beginning to brown on the edges, about 10-15 minutes. Remove from the heat. In a non-stick frying pan, spread the 1/4 c. sugar out in a single layer. Heat the sugar over medium-low heat, keeping a close eye on it but not stirring it. When the sugar begins to melt, use a rubber spatula to push the unmelted sugar into the melting sugar. Once all of the sugar is melted, add the pork belly and sauce and quickly stir to coat with the caramelized sugar, then add the lime juice. Cook until pork is fully coated and caramel sauce is thick, about 2-3 minutes, then remove from the heat and set aside.
To prepare the sandwiches, slice each baguette in half lengthwise. Mix the mayonnaise and sriracha together in a small bowl and spread on the bottom half of each baguette. Place a layer of sliced cucumbers on top of the mayonnaise, then top this with the pork belly. Place a few large spoonfuls of the pickled carrot and daikon on top of the pork belly, then top that with the cilantro leaves. Close the sandwiches and serve immediately.