Without voiding?? Well, bigger tires is about the only thing you can do safely. However, if you lift...and then bring it down to stock before taking it into your dealership, then it should be no problem.
Remember, the dealership has to PROVE that your modifications led to the problem to be able to deny your claim. So, if your exhaust blows, then they cannot deny the warranty fix because you lifted your truck.
Hope this helps.