Combine lemon juice, mustard, and garlic powder in a large bowl; reserve 2 tablespoons. Set aside. Add chicken to lemon juice mixture in large bowl, turning to coat. Cover and marinate in refrigerator 30 minutes.
Combine reserved 2 tablespoons lemon juice mixture, mayonnaise, barbecue sauce, chili powder, and paprika. Cover and chill.
Preheat oven to 400°.
Combine breadcrumbs and cheese. Remove chicken from bowl. Discard marinade. Dredge chicken in breadcrumb mixture. Place chicken on a broiler pan coated with cooking spray. Bake at 400° for 45 minutes or until golden brown and chicken is done. Serve with sauce, and garnish with lemon wedges, if desired.