Combine 2 tablespoons water and 2 tablespoons sugar in a microwave-safe glass measuring cup; microwave at HIGH 2 minutes.
Stir until sugar dissolves. Combine sugar mixture, orange juice, and next 6 ingredients (through chiles) in a blender, and process until smooth. Add ice to blender; pulse to combine. Stir in 1/8 teaspoon salt.
Chill in refrigerator 30 minutes, stirring after 15 minutes.
Combine remaining salt and 3/8 teaspoon sugar in a saucer. Rub the rims of 6 glasses with 1 lime wedge; spin rim of each glass in salt mixture to coat.
Fill each glass with about 2/3 cup margarita.
Note: Champagne mangoes are also called Ataulfo mangoes. Other varieties may be used but won’t be as smooth. Use more mango nectar to compensate.