So a few Vehicles have weapons classified as PG (Pintle mounted with a Gun Shield). Gun Shields don't appear to have any mechanical benefit other than blocking the users Arms from attacks (see the chart in the vehicle combat section for the various Weapon Mounts, gun shields are a single sentence at the bottom of the pintle section).
Is this intended to be intentionally vague? What's the amount of cover or armor that a gun shield provides mechanically? Typically gun shields are metal sheets that are sometimes ballistic rated and slanted to deflect incoming rounds away from the gunner. They also only typically provide cover for 90 degrees. They certainly wont stop a tank shell.
Also, there doesn't seem to be any rules for adding makeshift armor to vehicles, just repairing. I'm not sure if I missed that in the small crafting or Player Base sections, but unless adding extra armor to vehicles is just part of the Mechanic Archetype's flavor text, this is something that I hope gets expanded upon.