if using uncooked chicken, simmer the soup for longer, until it is opaque and cooked through.
you can also use shrimp or other shellfish, again adjust cooking time, as needed
Veggies: I prefer baby spinach, but kale, Swiss chard or other greens would work. Other options, peas, green beans, zucchini, cauliflower, broccoli, bok choy or Brussels, red, orange or yellow bell peppers, chopped tomatoes, etc