Uncle Base is a exciting addition to any campaign. Uncle Base is about growing and improving a personal hub world between missions.
In FIST, the death of a PC is fairly expected. The base in Uncle Base becomes like a 2nd character that the group shares. Even if your character dies a sense of progress can still be felt when a mission's loot creates new advancements for your base.
Aside from the many mechanical benefits your players can obtain from the content of this add-on, I find that hub worlds allow stories to easily integrate any kind of adventure, without having to strain story logic to make it happen. The promise of flexibility would make it an attractive option for all kinds of tables.