Usually I don't alter the gobjects.dcg or gunits.dcg files. According to my testing both stationary & moving objects seem to work all right even if not added to the vanilla files. The only thing (IMHO) the files affect is their infantry value points. As Lowengrin wrote:
"Each location can have "troops" at the location. These troop values are tracked in the locations.dcg. Basically, infantry is abstracted in DCG. Tanks have an attack value against them and a defense value - which is basically the most damage they can do to the infantry when the tanks are in an attack role or a defense role."
That means that those files are important if you use active front (front moves and locations change owner depending on ground battles). But even without them tanks and vehicles move, shoot, fight and are destroyed just as they should.
I usually determine location ownership changes solely by timetable commands so those files are not required for my campaings to work.