Don't let anyone ever tell you sandwiches are only for lunch and are not elegant. Sprouts and avocados can be quite elegant because they are "adult tastes". Sprouts are stringy and often odd to kids. Kids may eat guacamole, but without all the additional flavors, avocados can taste rough. When at peak season, with red tomatoes and fancy bread, such a meal can be very good. And let's face it, counselors on weight loss and proper digestion would recommend lighter compared to heavier dinners because people often get home late and generally have larger entree meals for lunch.
I recommend this simple sandwich on whole wheat toast with mayonnaise or oil and vinegar dressing and seasonings of choice: seasoned salt, Greek herbs, Italian herbs, onion powder, salt and pepper, the list can go on. Some individuals might go for lettuce, black olives, and cheese. No doubt the sandwich could turn into a "Dagwood". I see no problem with that as long as the bread can hold it all together and sometimes even if it can't.