Preheat the grill, setting the burners to high. Oil the grate.
Grill the onions for 8 minutes, the eggplant slices for 6 minutes and the bacon for 4 minutes, turning halfway through cooking, or until the vegetables are tender-crisp and the bacon is cooked through. Grill the buns, if desired. Set aside and keep warm.
Using lightly oiled hands or a hamburger press, shape the meat into 6 large patties. Place on an oiled plate and season with salt and pepper.
Grill the patties for 3 to 5 minutes on each side or until cooked through.
Spread the inside of the buns with the chipotle cheese sauce. Layer with the patties, grilled vegetables, bacon and lettuce.