Emmental can be replaced with cheddar, mozzarella, Gouda, Monterey Jack, or another good melting cheese.
For extra protein, use a high-protein bagel or add another egg.
If you prefer less heat, replace the spicy mayo with regular mayonnaise, garlic yogurt sauce, or another mild creamy sauce.
Fresh tomato, cucumber, arugula, baby spinach, or microgreens can also be added for extra freshness.