Honestly the requirement for S rank is sometimes rather lame, having 2 S ranks in enemies defeated and damage taken, then having 1 A rank because of time, making the mission an A Rank, it's like that 1 A rank over powers the 2 S ranks.
Hey they did a remake of Fire Emblem Gaiden with Shadows of Valentia. So it wouldn't be too far fetched to see a Blazing Sword remake, especially if the demand for such a remake is loud.