Theres quite a lot to address in the past replies to this thread. As such, I'll just copy and paste my take on a food system -
This idea originally spawned from when I noticed small towns and grasslands lacked stores, or anything beyond residential buildings. The idea is that you have to periodically go out and scavenge for food to support your settlement, as you're the only one who can leave. You could do this via fruit and berries in Grasslands with groves, finding them in abandoned stores (if they were ever added), so on and so forth. It would be immersive because the survivors you rescue would start seeming more alive.
To keep it balanced, and less intrusive, have each day the settlement goes without food, lower the tier at which they can perform at by 1, regardless of personality structures. When they reach 0, the Illari will put them in a state of suspended animation, to prevent them from dying, and you'd be unable to use any applying guardian scrolls until you've brought food. This way it isn't required that you keep food stockpiles up, just recommended. Perhaps the food could be visually seen, or just added to the supplies manifest when you enter the settlement chunk. (Maybe even a "retrieve food supplies" secret mission could seed periodically, to further make secret missions worthwhile to check out.)