Julhelm, I tried this once, even without any targets, just the terrain height and texture data. The big, I mean big problem is the 500 meters heightmap resolution for stock FE/FE2 terrains opposed to 2000 meters for jet titles, causing enormous slowdowns and display artifacts, I think this can be done, but involves a lot of trials and errors in flightengine and terrain_data. Draw distances are several times larger for SF2 compared to FE2. You'll hit the maximum vertex index for scene renderer fast, resulting in CTD.
The other way around it works without problems. You can allways try to retile, preferably by terrain_data.ini texture pointers change, given terrain (ie. GErmanyCE) using Jan Tuma's tileset, but you'll loose all his precious tods which are 500m resolution. Unless someone finally cracks the damn thing (tod 3D format) or make tool to rescale the tods. They are in fact single objects with subelement hierarchy.