Special equipment: hardwood charcoal; 4 cups applewood or mesquite wood chips, soaked in cold water for 1 hour
For the brine: Bring 8 cups water to a boil in a large saucepan. Add the salt and sugar and cook until dissolved. Add the fennel seeds, garlic, thyme and fennel fronds and remove from the heat. Let cool completely (or reduce the amount of water in the brine by 2 cups and add 4 cups ice cubes to cool down immediately). Transfer the brine to a plastic container, add the pork, cover and refrigerate for at least 1 hour and up to 4 hours.
For the smoked pork: Remove the pork from the brine, rinse well with cold water and pat dry. Put on a rack set over a baking sheet and refrigerate (to allow a crust, or skin, to form on the outside) for at least 1 hour and up to 8 hours.
Remove the grill grate and ceramic plate from the cooker. Add the hot hardwood charcoal and scatter the soaked wood chips over the top. Put on the ceramic plate and the grill rack, close the cover, bring the temperature to between 300 and 325 degrees F and allow to smoke for 10 minutes.
Brush the entire loin with oil and sprinkle with pepper. Place on the rack, close the cover and smoke until an instant-read thermometer inserted into the center registers 140 degrees F, 1 to 1 hour 30 minutes.
While the pork smokes, combine the balsamic vinegar and honey. Start brushing it on the pork about 30 minutes before it is done. When done, remove, loosely tent and let rest 10 minutes before slicing.
For the fennel gremolata: Cut the fennel into small dice and coarsely chop the fronds; put in a bowl. Add the zest and juice and drizzle with a little olive oil; mix to combine. Let sit at room temperature.
Spoon the Grape Mostarda onto a platter, top with the pork and spoon the gremolata over the pork.
Heat the canola oil in a large saucepan over high heat. Add the grapes, shallots, sugar, vinegar, mustard seeds, rosemary and 1/2 cup cold water. Bring to a simmer and cook until the grapes soften slightly and the mixture thickens, about 20 minutes.
Remove from the heat. Stir in the mustard and orange zest. Transfer to a bowl and let come to room temperature. Remove the rosemary sprig. Serve at room temperature.