If you move to a large home base (County Fair, or Snyder Truck Warehouse) with 8 outposts, you can set them all up around whatever base you plan to move to before you actually move. If you're moving into a base with a low maximum outpost count (usually for scavenging reasons) just make sure you have all 8 in place where you want them before you move, and then move to a place with a lower maximum outpost count. You will still have all 8 outposts.