Hot Chili Mayo: Stir all ingredients in small bowl. Season with salt. do ahead Can be made 1 day ahead. Cover and chill.
Meatballs: Line rimmed baking sheet with plastic wrap. Gently mix all ingredients in large bowl. Using moistened hands and scant tablespoonful for each, roll meat mixture into 1-inch meatballs. Arrange on baking sheet. DO AHEAD Can be made 1 day ahead. Cover and chill.
Sandwiches: Toss first 5 ingredients in medium bowl. Let stand at room temperature 1 hour, tossing occasionally.
Preheat oven to 300°F Heat sesame oil in large skillet over medium-high heat. Add half of meatballs. Saute until brown and cooked through, turning meatballs often and lowering heat if browning too quickly, about 15 minutes. Transfer meatballs to another rimmed baking sheet. Place in oven. Repeat with remaining meatballs.
Cut each baguette or baguette piece horizontally in half. Pull out enough bread from each bread half to leave 1/2-inch-thick shell. Spread hot chili mayo over each bread shell. Arrange jalapenos, then cilantro, in bottom halves. Fill each with 1/4 of meatballs. Drain pickled vegetables; place atop meatballs. Press on baguette tops.