Combine broth and 1-3/4 cups water in a bowl; set aside. Heat 2 tablespoons oil in a 6-quart stock pot over moderate heat. Add onion and cook, stirring occasionally, until softened but not browned, 3 to 4 minutes. Stir in 1/4 teaspoon salt and the rice. Add wine and 3 cups broth mixture; bring to a boil. Reduce heat to a simmer and cook, stirring occasionally, until liquid is absorbed and bottom of pot is dry when rice is pushed to the side with a spoon, about 10 minutes.

Meanwhile, whisk together remaining 3 tablespoons oil, 1/4 teaspoon salt, the vinegar and pepper in a small bowl. Toss in tomatoes and basil; set aside.

Add broth mixture, 1/2 cup at a time, to rice (allowing liquid to absorb after each addition), stirring frequently, and cook until rice is al dente and creamy, 10 to 12 minutes. Additional water may be added, 1/2 cup at a time, if needed. Stir in corn and 1/2 cup water; cook until heated through, about 1 minute.

Remove from heat, stir in cheese and salt to taste. Divide risotto among 4 shallow bowls or plates, to with chicken and tomato mixture. Serve immediately with additional cheese on the side.