Entirely new areas are not possible, without a proper TERRAIN EDITING/CONSTRUCTING PROGRAM, which no one has coded so far. Those "map.pk2, *.o2" file editors are just horsecrap.
If you want to copy regions, just take an example of the Jupiter regular region and mirror world region. Those are fairly cloned.
Yes, you actually can. The current map editor tool (which has been released) does place objects into the world, but without any collision, which means, you will walk through anything you've placed on the map.
There is also another version which has that feature, but is not public at the same time.