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