For the dressing: In a small bowl, combine the vinegar, lemon juice, hot sauce, garlic, salt and pepper. Gradually add the oil, whisking until the dressing is thick.
For the salad: In a large bowl, combine the chicken, arugula, avocado, fennel, feta, spicy sweet peppers, sun-dried tomatoes, salt, and pepper. Add the dressing to the salad and toss to coat. Fill the lettuce leaves with the salad. Arrange the lettuce leaves on a platter and serve.