Mix sugar, chopped mint, basil and lime peel in medium bowl. Mash with wooden spoon until herbs turn dark green, about 3 minutes. Stir in lime juice and 1 1/4 cups water. Let stand 1 hour. Strain into large bowl, pressing on solids. Transfer 1/2 cup lime syrup to small pitcher; cover and refrigerate. Pour remaining lime syrup into 13x9x2-inch metal baking dish. Place dish in freezer. Stir syrup with fork every hour until frozen, about 4 hours. DO AHEAD: Can be made 1 day ahead. Cover and keep frozen.
Divide melon wedges among 8 shallow soup bowls. Drizzle melon with reserved lime syrup. Scrape granita into flakes with fork. Spoon generous 1/2 cup granita atop melon in each bowl. Sprinkle with sliced mint leaves, garnish with mint sprigs, and serve.