The actual map displayed in DCS/LOMAC FC is actually closer to 800km x 1100km as it encompases the entire Black Sea Region. The detailed map is finite though because of the large number of objects like rivers, roads, buildings, farms, airbases, etc so its comfined to mostly Russia and Georgia.
I agree there should be support for larger maps, but I'm comfortable with having a map pulldown list like in IL-2. In older games like Janes F-15, the maps were so large that some flights took 5+ hours... I'm not sure how many of us have that much time to devote on a weekend with real life obligations ;)