Slice the skirt steak into 4 equal pieces and place in a large sturdy resealable plastic bag. Set aside while you make the marinade.
In a jar with a tight-fitting lid, combine the juice of 4 limes, the soy sauce, tequila, if using, Worcestershire sauce, garlic, cumin, Traeger Chipotle Rub, salt, and 1/2 cup vegetable oil. Shake vigorously, then pour over the meat.
Massage the bag so all the meat is coated. Seal and refrigerate for 4 to 8 hours. (Any longer, and the texture of the meat changes due to the acids in the marinade.)
When ready to cook, put a large well-seasoned cast iron skillet on one side of your Traeger. Start the Traeger on Smoke with the lid open until the fire is established (4 to 5 minutes). Set the temperature to High and preheat, lid closed, for 10 to 15 minutes.
Drain the steak (discard the marinade) and pat dry with paper towels. (You'll get a better sear if the outside of the meat is not wet.) Season with Black Pepper, freshly ground. Add the remaining tablespoon of oil to the skillet.
Arrange the steak on the grill grate. At the same time, add half the bell peppers and onions to the hot skillet. Grill the steaks, turning once, for 2 to 3 minutes per side, or until done to your liking. Stir the vegetables to lightly char them, 10 to 12 minutes.
Transfer the steaks to a large platter and cover loosely with aluminum foil. While they rest, finish sauting the first batch of vegetables and add to the platter with the steak. Saut the remaining vegetables in the skillet. Toast the ciabatta rolls, if desired, by grilling them for several minutes, cut sides down.
To serve, thinly slice the steak against the grain and arrange on one side of the platter. Pile the peppers and onions on the other side. (Alternatively, serve the sliced steak and vegetables directly from the hot cast iron skillet.)
Garnish the platter with cilantro leaves. Wrap the ciabatta rolls in a cloth napkin and serve in a basket alongside the meat and vegetables. Serve with any or all of the condiments suggested above.