1. Cook pasta according to package directions, adding green beans to boiling water during last 2 minutes of cooking time; drain. Rinse pasta mixture with cold running water; drain well.
2. Place pasta mixture, thyme, and 3 tsp. lemon zest in a large bowl; toss gently to combine.
3. Whisk together pistachios, next 5 ingredients, and remaining 2 tsp. lemon zest in a small bowl. Add oil in a slow, steady stream, whisking constantly until blended. Drizzle over pasta mixture. Add arugula, and toss gently to coat. Serve with desired toppings.
*Penne pasta may be substituted.