Put the steak in a zip-top bag. Pour over 1 cup of Fig BBQ Sauce, then seal the bag, removing as much air as possible before closing. Marinate the steak in the refrigerator at least four hours, or let it marinate overnight.
Heat the grill to medium (350 degrees).
Wipe the marinade off the steak, then sprinkle with salt and pepper. Discard the marinade.
Grill the steak and the red onion rings until the steak is cooked to your liking (about 12 minutes for medium-rare and the onions have grill marks and are starting to soften. Let the steak rest about 10 minutes, then slice thinly against the grain.
Cut the French bread into four pieces, then split each piece lengthwise (4 sandwiches). Spread the bread with butter, then toast briefly on the grill, about 30 seconds.
Assemble the sandwiches: Pile the lettuce, sliced steak and grilled onions on the bread, then top with the halved figs, crumbled goat cheese, and more Fig BBQ sauce.