You can have one save file dedicated to a "World Title" and another dedicated to a "Tag Title." You can simulate a "Promotion vs. Promotion" event by loading a champion from a different save file (simulating an invasion) and having them defend their title against your home promotion's champion. The save file acts as the "contract" for the match.
Managing these files usually requires specific software to convert or move them: Fire Pro Wrestling Returns Saves
If you are playing Fire Pro Wrestling Returns on the PCSX2 emulator, installation is trivial. You can have one save file dedicated to