Mix together olive oil, vinegar, oregano and thyme in a shallow dish. Add tomato slices and turn to coat. Season with salt and pepper to taste. Let tomatoes marinate up to two hours.
Place oven rack in center of oven and preheat to 400°.
Place bacon slices on a broiler pan (or cookie sheet lined with foil). Mix together brown sugar and black pepper. Sprinkle each bacon slice with brown sugar mixture to cover. Bake bacon 15-20 minutes until golden brown and crispy. If using cookie sheet, transfer bacon to sheet lined with paper towels to absorb excess fat.
In a small bowl, stir together mustard and jam.
To assemble sandwiches, spread cut surfaces of all 4 croissants with fig mustard. Layer on 1 slice of cheese, avocado slices, cucumber slices, marinated tomatoes, lettuce leaves, 3 strips of candied bacon and a final slice of cheese.