Prepare tofu: Cut tofu into 7 or 8 slices, each 1/2-in. thick and about 4 by 2 in., and set in a 9- by 13-in. dish. In a food processor, whirl lemongrass to mince; set aside 1 tsp. Whirl ginger and garlic with remaining lemongrass to mince. Add 2 tbsp. water and the remaining tofu ingredients; whirl to blend. Spoon marinade over tofu and turn to coat, distributing seasonings. Chill, covered, at least 3 hours, turning occasionally.
Meanwhile, make sauces: In a small bowl, combine hoisin, reserved lemongrass, and the ginger. In another small bowl, combine mayonnaise and chipotle. Chill.
Finish sandwiches: Preheat oven to 450°. In a bowl, combine carrots, daikon, and vinegar; set aside. Set tofu on an oiled baking sheet, brushing off seasonings with fingers. Bake tofu until browned and a little crisp, 25 to 30 minutes. During last 5 minutes, set bread on oven rack to crisp.
Brush tofu generously with hoisin sauce. Split bread lengthwise and spread cut sides with chipotle mayo. Overlap tofu on bottom of bread. Drain carrot mixture (pat dry if quite wet) and arrange over tofu with cucumber and cilantro. Set top of bread in place and secure sandwich with short skewers. Cut into portions.
Make ahead: Through step 2, up 1 day, chilled.