I like MGS references that aren't just blatant ripoffs.  This add-on fits the bill.
I like well-laid-out tri-folds, with their tight data presentation and tactile element.  This add-on fits the bill.
I like systems that allow the Ref to build layers of success into a mission, so each op isn't an all-or-nothing affair.  This add-on fits the bill.
I like having optional Troupe Play rules to shake things up while maintaining stability and player control.  This add-on fits the bill.
I like supplements that reference other supplements to save on redundancy, but are still built so that if you don't have that other thing you can improve/reason your way through it anyway.  This add-on fits the bill.

This add-on fits the bill.

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.

Uncle Base is an expansion that adds basebuilding to FIST. It's also a direct continuation of the adventure in Rations #2 in the mainline game.

The PDF is 2 pages, with cleanly organized text, some nice graphics, and an action-movie-y feel.

Contents-wise, Uncle Base leans in on the Metal Gear overtones of FIST and gives the players their own outpost to develop. Missions now award money and construction crates. Crates can be used to build base facilities. Money can be used to buy crates or other rewards. The PCs can also recruit new agents to the base and dispatch them on missions.

Everything in this supplement feels rewarding to include, and growing the base gives FIST a Blades-In-The-Dark-esque gameloop. For players that like to chase the dopamine of progression, this is a VERY good add-on for your FIST game, but it's also just a nice backbone of structure for any FIST campaign.

Overall, this is a short module, but it's packed full of content. If you're interested in running FIST as a campaign---or even as just a regular series of one-offs---I'd strongly recommend including Uncle Base in your material.