Marinate: In a large bowl, add buttermilk, shrimp, hot sauce, ½ teaspoon of garlic powder, ½ teaspoon of onion powder, and 1 teaspoon of salt. Stir, cover the bowl with plastic wrap, and put in the fridge for an hour.
Breading: Place ¾ cup of flour in the first bowl. Beat an egg in the second bowl. Mix panko, cornmeal, ¼ cup of flour, thyme, oregano, ¼ teaspoon of garlic powder, ¼ teaspoon of onion powder, cayenne pepper, and ⅓ teaspoon of salt in the third bowl/plate.
Dip the shrimp in the flour then shake off any excess. Dip them in the egg and again shake off any excess. Coat the shrimp with breadcrumbs then gently shake off excess. Put the breaded shrimp in a fridge for 15 minutes.
Frying: In a large dutch oven, heat 2-inches of oil over medium-high heat to 350°F. Working in batches, fry the shrimp until golden brown for 2-3 minutes or until fully cooked. Transfer the shrimp to the paper towel-lined plate to drain.
Building: Toast the bread and spread the remoulade sauce on both halves of the rolls. Put fried shrimp on the bottom half then layer with sliced tomatoes and chopped lettuce. Put the other slice of bread on top.