You could simply "privatize" the post office and that'd remove half the federal work force ~ and have absolutely no impact whatsoever over the power and scope of the federal government.
Like hell. At the end of the month, when pension checks are due, welfare checks are due, the postman is the most important person in the world. If you think you are going to win public support by making old people and welfare people walk 5 miles to pick up their welfare checks, good luck! You can fire them for the rest of the month though.