Also, your survivors should age so for example your leader dies and another person takes his/her place. This will help increase the rate of this game because it will be very realistic and people don't see that in many games :)
I think to make this game very realistic and different and better from other games there should be emotional feelings between the survivors.
For example, one of your fighters might not like your scavenger. This could mean that putting these two together on the same mission would reduce the success rate because they don't get along together. However, sending people that get along together on the same mission should increase the success rate and also increase loot or mission exp etc.
Another point I will like to make is allowing survivors to make love between each other. This way they can have children which will possibly increase the morale of the survivors and after a certain time the baby can grow up and help you with figthing.
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