Lightly coat a medium saucepan with cooking spray. Add the finely chopped onion and ginger. Cook until tender, stirring occasionally. Stir in catsup, apricot preserves, orange juice, Worcestershire sauce, and pepper. Bring to boiling; reduce heat. Simmer, uncovered, about 10 minutes or until sauce is slightly thickened.
Cover and refrigerate the sauce for up to 3 days.
For onion medley, tear off a 48x18-inch piece of heavy foil. Fold in half to make a double thickness of foil that measures 24x18 inches. Spray foil with nonstick spray coating. Place sweet onions, red onion, green onions, leek, and garlic in center of foil. Drizzle with olive oil. Sprinkle with thyme, salt, and pepper. Bring up two opposite edges of foil and seal with a double fold. Fold remaining ends to completely enclose the vegetables, leaving space for steam to build. Grill foil packet on the rack of an uncovered grill directly over medium coals about 30 minutes or until onions are tender.
Place chicken on grill rack directly over medium coals; grill for 12 to 15 minutes or until chicken is tender and no longer pink, turning once halfway through grilling and brushing with sauce the last 5 minutes.
Slice barbecued chicken diagonally into thin strips; set aside.
Place bread shell on a pizza pan or baking sheet. Spread barbecue sauce over shell or crust to within 1/2 inch of the edges. Sprinkle with half of the mozzarella cheese. Sprinkle Roasted Onion Medley atop cheese. Arrange chicken strips and nectarine or apricot slices atop onions. Sprinkle with remaining cheese.
Bake in 400 degree F oven about 15 minutes or until pizza is heated through. Cut pizza into wedges. Garnish with fresh thyme leaves, if desired. Serve immediately. Makes 6 servings.