JALAPENO Mayonnaise: Process juice, peppers and garlic in food processor until peppers are minced. Add mayonnaise and seasonings; process until well blended. Refrigerate until ready to use.
STEAK Marinade: Mix vinaigrette and mustard; pour over steaks in shallow pan. Turn to coat both sides of each steak. Refrigerate up to 4 hours to marinate. Remove steaks from marinade; discard marinade.
FOR each serving: Grill 1 steak on medium-high heat 5 to 7 min. or to medium doneness, turning once. Remove from heat; let stand 5 min. Cut across the grain into thin slices.
PLACE bottom half of 1 sandwich roll, cut-side up, in half-sheet pan; cover with meat and 1 cheese slice. Bake in 325ºF convection oven 2 min. or until cheese is melted. Meanwhile, spread 2 Tbsp. Jalapeno Mayonnaise onto cut side of top of roll.
TOP sandwich with 2 tomato slices, 1/2 cup lettuce, 4 avocado slices and 1 tsp. cilantro; cover with top of roll.