Honestly regarding Fire Emblem, I think Celica would also be a good legacy character and probably a better one than Lyn moveset wise as she uses Swords and Magic in her base and would also be a good choice for those that want to replace Robin whom I'd argue is up there with Chrom as the most likely to get replaced by another character. My reason for saying that is that since Awakening is no longer the biggest game in the franchise, it doesn't need 3 reps and Lucina is by far the most popular of the 3(Ike, Lyn, Lucina and Roy, are all the 4 most popular characters actually) as well as the one who'll have more appearances and importance in the series like Engage for Example.
These videos are really fun. Harry from Teleroboxer would be a great retro pick I think.
Honestly regarding Fire Emblem, I think Celica would also be a good legacy character and probably a better one than Lyn moveset wise as she uses Swords and Magic in her base and would also be a good choice for those that want to replace Robin whom I'd argue is up there with Chrom as the most likely to get replaced by another character. My reason for saying that is that since Awakening is no longer the biggest game in the franchise, it doesn't need 3 reps and Lucina is by far the most popular of the 3(Ike, Lyn, Lucina and Roy, are all the 4 most popular characters actually) as well as the one who'll have more appearances and importance in the series like Engage for Example.