Prepare the crab mayo. Drain crab meat. Mix with mayonnaise and lemon juice in a medium bowl. Season with salt and pepper. Set aside.
Combine cornmeal with garlic salt and Old Bay seasoning. Dip shrimp in the whisked egg and dredge in the cornmeal batter. Carefully drop shrimp in the hot oil and fry until golden brown. Remove from oil and transfer to paper towel lined paper.
Assemble sandwiches. Spread crab mayo on each of the toasted hoagies, followed by romaine lettuce and ½ an avocado per sandwich. Season avocado with salt and pepper. Top the sandwich with 5 shrimp each. Drizzle Louisana hot sauce if desired and serve.