Changing the tiles is a easy job but the destructibles etc is alot harder. if I were you I would just split the map into 2 instead and have blockers so people think when they see the whole map they only see half and the other half is hidden by view blockers and then you have the units created on 1 of the 2 sides and the camera taken there. Making 2 sets of terrain would take alot of work and probaply in the end take up as much of space as creating 2 terrains and having view blockers.