For the relish, in a large bowl, whisk together the vinegar, oil and sugar. Add vegetables to bowl and toss with dressing and celery seed; season with salt and pepper. Let the relish stand 30 minutes. Drain.
In a cast-iron or other deep skillet, heat the oil over medium-high. Melt the butter into the oil. When the butter foams, add the meat; season with salt and pepper. Cook, breaking the meat up with a spoon, until brown, about 10 minutes.
Add the onion, garlic, chiles and allspice. Cook, stirring often, until the onion softens, 5 minutes. Stir in the tomato sauce, stock, hot sauce, brown sugar and Worcestershire sauce. Reduce the heat to low and simmer until thickened, about 2 minutes.
Serve the meat piled on the rolls, topped with the blue cheese and relish.