Glad you liked the game. While the game made a profit, there wasn't enough sales for them to make it worth making a sequel.
I thought of making a mod to make it open ended at one time, but the problem is by the end of the game there is no where else to explore. There are no places to loot and nothing new to investigate. The game was about exploring the way humans act in a crisis so it was made with a tailored story and locations in mind. There isn't any random maps beside the few random encounters. Unfortunately, a sandbox what not the kind of gameplay the devs wanted to make.
i assume there havent big enough sales because of the engine, lot of people had problems with hardware configuration, the game run bad sometimes, but definitely the devloppers should think about dead state 2, changing the engine and making more improvments
making the game sandbox or rpg somehow (a good engine to suggest Living World Architecture (LWA) ), with a lot of quests, start the camp from a school and be able to move and settle in another location like prison or army base until found by enemies or attacked by hordes
form squads of scavengers or fighters or guards, buildings or departmenets inside the shelter, schools, training, hospital, etc...