With Better GridDef, the "+3 Grid Def" pilot rankup bonus is renamed into "Grid Shield". Every pilot with the Grid Shield bonus will grant a random building on the map a protective shield at the start of the mission. The Grid Shield bonus also provides an extra 3% Grid Defense.
In case this buff isn't enough for you, there's also the option to increase the number of shields granted by Grid Shield. There's usually 7 or 8 building tiles on the map every mission, so if you want to turn up the power you can make it quite the useful bonus. The default is just 1 though, it's already been useful enough in my test campaigns. If you want to change it, however, you'll need to start a new timeline unfortunately.
Known Issue: On easy single-reward missions where some of the buildings already have shields, only a few of the Grid Shields will properly activate. This is because shielding an already shielded target does nothing, and Subset shockingly never coded a way for us to check if a building is already shielded. So I can't exclude already shielded ones from the target list.
1. Make sure Into the Breach is up to date.
2. Find your Into the Breach directory. If you are playing ITB under Steam, this directory can be found via Steam Library -> Right Click Into the Breach -> Properties -> Local Files -> Browse Local Files.
3. Scroll down to the download on this page, and follow the instructions there to install the mod loader.
4. Download this mod (link below) and unzip/extract it to the mods folder inside your ITB directory.
5. Run the game!