In a bowl, whisk together mayonnaise, mustard, vinegar, and sugar. Stir in black pepper, salt, onion powder, and celery seeds. Fold in the coleslaw mix, cover, and refrigerate for at least 1 hour.
Preheat the Blackstone griddle to high heat.
Divide the ground beef into four equal portions (about 4 oz each) and shape into patties. Season one side of each patty with SPG or salt, pepper, and garlic.
Drizzle oil on the griddle, place the patties seasoned side down, and season the other side.
On another section of the griddle, heat the pulled pork with a little oil, stirring as it warms.
Spread butter on one side of each slice of Texas toast. Place the bread butter-side down on the griddle and flip until golden brown on both sides.
Flip the burger patties once the first side is seared. Reduce the heat slightly, then top each patty with one slice of Swiss and one slice of cheddar. Add a portion of pulled pork on top of the cheese. Drizzle a little water on the griddle and cover with the lid for 1–2 minutes to melt the cheese.
To assemble, place a slice of toasted bread on a plate. Spoon coleslaw on top, add hot pickles, then place a cheesy pulled-pork-topped patty. Drizzle with barbecue sauce and finish with a second slice of toasted bread.
