I looked Tyler Florence's recipe for chiles rellenos, and I think you can make some variations to it to make it ww friendly:
To fill them, you can substitute the corn for zucchini/mushrooms.
Instead of making the flour-beer batter, you can whip some egg whites to hard peaks, and if you dry COMPLETELY the chiles and the filling is dry enough, the egg whites should cover completely the chiles and wonít fall easily, or try sprinkling the chiles with very little whole wheat flour before covering with the egg whites.
If you charred them well enough and let them sit wrapped in a plastic bas, then a tea cloth, and then in plastic again and let them cool completely, they will be cooked enough so you donít need to deep fry them to complete the cooking.
Instead of deep frying them, use a very hot non-stick surface with very little oil, and turn them carefully to avoid breaking the egg whites.
To serve them, instead of sour cream, try making some tomato sauce (fry with as little oil as possible some sliced onion, add tomato puree or natural chopped ones, salt, pepper, fry until color changes and add little water to it).
This way I think all the points you might have to calculate are the ones for the oil, egg whites, and whole wheat flour if you used it.
You can also fill them with tuna, refried beans, panela cheese (softens but doesn't melt), minced meat...
Hope this helps...