I have a world I had toyed with where our world is invaded by creatures very vaguely like the heartless from kingdomhearts. The creatures are mostly immune to traditional weapons, as regular matter seems to pass through them while doing very little harm. These creatures are made out of a sort of mental energy humans can create and are trying to capture humans of our world so the creatures can 'reproduce' by using captives to generate more of this energy.
When a human Falls to these creatures they don't die, instead, they are pulled into a sort of parallel pocket dimension and held in suspended animation where they can be used as a metaphysical battery pack. If all the shades invading a world are destroyed they will be unable to hold this pocket dimension in place and all the people that Fell to them will reappear on earth as if they were never gone.
This was discovered the hard way when the first world in my story barely drove back these attacking creatures only to have a large percentage of the world population reappear all at once. This leads to anarchy and significant problems, not the least of which being there was no longer enough food being produced to feed the now reappearing people causing issues with starvation. However, other issues have come up such as arguments over who 'owns' a property that was originally owned by someone who Fell and his estate sold off his property. Even the question of who is the leader of a given country is up in the air, as some leaders Fell and were replaced during the fighting.
Our heroes have now travelled to a parallel world that they can tell is being invaded by the same creatures. The heroes plan to aid in defense of this world and teach its inhabitants how to make weapons capable of harming the creatures (...and to decrease the demand for food in their homeworld by moving some of them off to another world with sufficient production to feed them).
This new world will fair far better than the first, having been taught how to make weapons to fight the creatures much earlier into the invasion. The second world will also benefit from gaining all the tactics and lessons learned from the first invasion, and inventing some further tactics over the course of the fighting. Far fewer of this second world will fall, and within roughly a year the enemy will be driven back.
My question is how should this second world handle those that Fall during a fight? It's fully anticipated they will eventually win the fight and that all those that Fell will reappear one day, though they don't know exactly when that will happen. They also know the chaos caused by this reappearance the first time around and so will have to make laws and policies for handling Fallen individuals return in hopes of minimizing problems when they return.
What kind of laws should be in place to handle this issue? What will be done with property owned by someone who has Fallen? Does a family of a Fallen solder get paid a death gratuity still? Will I be guaranteed a job after I return from Falling, and how can the labor market survive the influx of new workers?
Of course, there will have to be plenty of work done to ensure that the food supply can survive the reappearance of hungry mouths, though I imagine simply providing government stipends and support to keep farms, and other food sources, running despite lower demand and canning or otherwise preserving excess food generated should help ensure enough food is available originally to feed those that reappear and that it's not too hard to ramp up food production...
I'm looking at policies that would be made by first-world developed nations, as they are more in focus to the story. However, some of those policies may include setting up systems to support less developed nations which are likely to struggle more when the Fallen reappear.
