This what I imagine for a remake of Fire Emblem : Genealogy of the Holy War. For the title i'd propose  Fire Emblem Echoes : The Holy War Saga.   First I would keep the size of the map but I would add some elements like secret dungeons or caves. I would include an avatar but he (or she) would an apprentice to one of Sigurd's knights. I think it is the best way to include a time pulse like mechanic. The avatar's Holy blood is Sothis Holy Blood, it allows the users to use