The thing is, that is has been done in games already prime example is Life is Fedual, which was made in Torque 3d game engine. I to have been trying to implement this into a game that i am creating. From my understanding is that it uses a procedural voxel terrain that can be manipulated by the player in game using various in game tools (shovel, pickax, etc) and on a multiplayer platform. I have for a few years been trying to find and understand this setup, coding and use in a game with little success myself. it is very limited subject in the community. I hope someone will post some tutorials on how to set this up in a UE4 engine or Unity3d.