It's not possible to move through maps in multiplayer unfortunately ;/
If you want to implement idea like Warcraft3 TFT orc additional camaign has (Rexxar one) you are forced to create signle-player map only and work with game-caches. You can see how blizzard is doing that in thier campaign, if you open given campaign from war3 folder.
Although, you can always divide your map into differend areas, use pathing blockers/terrain/cliffsv to prevent players from entering areas that they are not allowed to enter and use one of save/load systems to make game's appearance even greater.