For the pickled vegetables: Whisk the vinegar, honey and 1/2 tspkosher salt together in a medium bowl. Add the carrots, daikon and onion; toss gently. Refrigerate at least 30 minutes; stir occasionally to evenly distribute the brine.
Preheat your oven to 450 degrees F. Place the cubed baguette on a baking sheet and drizzle with a little bit of olive oil. Lightly season with kosher salt and black pepper to taste. Toss with your hands. Shake the pan so that the bread is in a single layer, then toast in the oven for 5-10 minutes, until lightly browned and crispy. Remove the croutons from the oven and transfer to a plate or bowl. Carefully dust off any crumbs from the baking sheet, then spray it generously with cooking spray.
In a large bowl, combine the beef, garlic, basil, up to 1 tablespoon sriracha sauce, black pepper to taste, fish sauce and kosher salt. Gently shape the meat mixture into 16 evenly sized meatballs and transfer each to the greased baking sheet, making sure to space them evenly apart so they are not touching. Bake the meatballs, undisturbed, until browned and just cooked through, 8-12 minutes. Let them cool a slightly while you assemble the salad.
At this point, add the mayonnaise and 2 tsp sriracha to the pickled vegetables and stir to combine thoroughly.
In a large salad bowl, add the romaine, cherry tomatoes and cucumber. Add the pickled dressed vegetables and toss to combine and dress the salad. Add the croutons and toss gently again. Divide the salad among dinner plates and top with 4 meatballs apiece. Drizzle with sriracha if desired, then garnish with the herbs and lime wedges. Serve immediately.