Combine first 6 ingredients; remove 1/2 cup mixture, and chill.
Place pork in a shallow dish or heavy-duty zip-top plastic bag; pour remaining sesame mixture over pork. Cover or seal, and chill 3 hours.
Cut squash into 1/2-inch slices, onions into quarters, and bell pepper and pineapple into 1-inch pieces. Arrange vegetables in a grill basket; set pineapple aside.
Grill vegetables over medium-high heat (350° to 400°) 15 to 20 minutes, turning occasionally and basting with half of reserved sesame mixture. Remove vegetables from grill basket.
Remove pork from marinade, discarding marinade. Arrange pineapple and pork in grill basket.
Grill over medium-high heat 4 minutes on each side, basting with remaining sesame mixture.
Toss together vegetables, pork, and pineapple. Serve mixture over saffron rice, if desired. Garnish, if desired.