Rub the chicken pieces all over with the orange juice, mustard, garlic powder, cumin, black pepper, all purpose seasoning, and salt. Cover and rest 30 minutes so the flavors sink in.
Heat the oil in a large pot over medium high heat. Sear the chicken a few pieces at a time until browned on all sides. Set aside.
In the same pot, add the tomatoes, garlic, green pepper, California chiles, and onion with enough water to cover. Simmer until everything is soft, about 15 minutes. Meanwhile toast the relajo mix in a dry skillet until fragrant, about 1 minute, stirring constantly so it does not burn.
Blend the softened vegetables with the toasted relajo, the uncooked rice, and 2 cups of water until completely smooth. Pour the sauce back into the pot over the chicken, add salt, and simmer covered on low heat about 1 hour, until the chicken is fall apart tender.
Lift the chicken out, pull the meat from the bones, and return the shredded meat to the sauce. Keep warm.
For the escabeche, pour boiling water over the shredded cabbage and carrot, drain well, and toss with the onion, cilantro, salt, pepper, and enough mayonnaise and mustard to coat lightly.
Slice the rolls open from the side without cutting all the way through. Toast them lightly until golden. Spread the inside with mayonnaise and mustard.
Line each roll with a lettuce leaf to protect the bread. Add a generous scoop of chicken with sauce, then the escabeche, cucumber, tomato, beet, watercress, and egg if using. Serve right away while the chicken is warm.