I think they should do a basic world map. Not even stock FSX quality, without houses and so on, based on some Open Street Map or something. About 10-20GB big. With a few airports (basically copy Kolkhi or so) around the world (a few on every continent) so you can just takeoff and fly somewhere.
That way realism fans could do realistic distances, and everyone else wouldn't care because they never see the map, because they start on the maps they bought. It will probably look fine on high altitudes anyway.
If some mission designer places objects there only he is to blame.
If you have a DLC map such as Nevada, it is loaded once you get "near", if you don't have it nothing happens, except online.
When online: The mission designer can determine needed DLCs, and you cannot join, so you can't have an advantage by flying a mission over an "empty" map with wrong elevation and a basic texture. A simple window tells you.