Sauté onions with butter, salt, pepper, thyme, and brown sugar until caramelized, about 30 minutes.
Add balsamic vinegar and stir.
Season pork chops with salt, pepper, and thyme. Grill until internal temperature reaches 145°F, about 10 to 20 minutes. Slice pork into strips.
Brush pizza crust with oil and lightly grill until charred and bubbly.
Top pizza crust with caramelized onions, barbecue sauce, pork, cheese, green onions, bacon, and apple slices.
Return to grill with the lid closed for 5 to 10 more minutes, or until cheese is melted.
Top with additional barbecue sauce, if desired.