I think you should go with how you added Infinity Aircrafts, adding the Original aircraft and the tagging the other variants with its skin, but this time next the JP (Japanese version only skins), add next to it (JP Only)
Example:
Add the F-16XF Gyrfalcon As a main page name, and then add that is has a variant called F-16XFU (JP), and just add the photo and other details of the variant in its own subject.
Edit:
For the other example were the main version is available in the JP version of the game, take the International as the main one, but just mention the this specific aircraft exists only in the JP version and it has a version in the International version.