I live in Chicago and deal with package theft at least once a year; this thought of dummy packages is not realistic and I'd never participate.

A more realistic solution: Package drop boxes. They can be either key or one-way door to help deter theft, and provide an added benefit of protecting a package against the elements.

Obviously, all packages weren't sized equal, but if you're having things delivered regularly, you can determine the type of cubic storage you'd need for a drop box to cover the majority of your deliveries.