It is possible. One could get all the data and convert it into a single huge map by joininig 3 or 4 maps. But it would take 100GB+ to load every time you start a scenario.
There is of course a lot of room for optimization if you take into comparison world scale rendering like X-Plane 11 or Flight Simulator 2020 which most of the time, with addon airports, often look better than DCS (At the cost of very low fps in VR - currently).