In a large nonreactive container, combine the water, kosher salt, and brown sugar. Stir until the salt and sugar crystals dissolve.
Add the onion and the pork chops. Make sure the chops are submerged in the brine. (You can weight them with bags of ice.) Cover and refrigerate for 4 to 8 hours.
When ready to cook, start the Traeger grill on Smoke with the lid open until the fire is established (4 to 5 minutes). Set the temperature to 450F (or High) and preheat, lid closed, for 15 minutes.
Drain the pork chops and rinse well under cold running water. Pat dry. Season the chops on both sides with black pepper. Discard the brine.
Place the lemons and orange half, cut sides down, directly on the grill grate. Roast for 15 minutes. Transfer to a plate and let sit until cool enough to handle.
Over a bowl, juice the lemons and the orange; you should have 5 to 6 tablespoons of juice; discard any seeds.
Finely dice enough citrus rind for 2 tablespoons. Add to the bowl along with the shallot, vinegar, honey, and salt and pepper. Whisk to mix. Slowly whisk in the olive oil. Stir in the parsley. Taste, adding more salt and/or honey if needed.
In the meantime, arrange the pork chops on the grill grate and grill, turning once or twice, until the chops are nicely browned and register an internal temperature of 145F on an instant-read meat thermometer (about 15 to 18 minutes, total).
With tongs, transfer the chops to a platter and let rest for 3 minutes. Drizzle with the vinaigrette; serve the remaining vinaigrette on the side.