Combine water and rice in a small saucepan, and bring to a boil. Cover, reduce heat, and simmer for 20 minutes.
Melt 3 tablespoons butter in a large saucepan over medium heat. Mix flour into the butter slowly, stirring constantly. Whisk in milk a small amount at time until smooth. Cook over a medium heat until thickened, stirring constantly. Stir in 1 1/2 cups shredded Swiss cheese, salt, pepper, and hot sauce; stir until the cheese melts. Stir in spinach.
Meanwhile, heat oil in a skillet over medium heat. Cook onion, garlic, bell pepper, and corn in oil until tender, stirring frequently.
Preheat oven to 350 degrees F (175 degrees C). In a large casserole dish, combine rice, spinach-cheese mixture, and onion mixture. Sprinkle breadcrumbs over the top of the casserole, dot with 2 tablespoons butter, and top with remaining 1/2 cup of cheese.
Bake, uncovered, in the preheated oven for approximately 20 minutes, or until cheese topping melts.