I’ve had this idea even before I finished playing FE7.
Story: After the events of FE7, Erk and Serra are about to wed. However, a magic portal opens and teleports them to another world. This world is full of demons, monsters, etc. The leader of this world, who happens to be a demon himself, is experimenting with magic portals (the same kind of portal that transported Erk and Serra) so himself and his demons can take over and destroy the human world of FE7. It is then up to Erk and Serra to navigate this world and stop the head demon.
Gameplay: The game is for two players. The player controlling Erk must run around attacking enemies with magic (he has unlimited magic). The player controlling Serra must heal herself by standing still; she can heal Erk by the two of them standing next to each other for a short while (she too has unlimited magic). But why do we need a healer? Because the enemies and bosses of the game have a few unavoidable attacks. Thus, it is important if both players can effectively dodge as many attacks as they can while finding moments in the enemy patterns to heal.
Thoughts?