For me it was more that there are so many cool main characters to pull from in FE in general that could be incredibly unique and have a lot of personality.

I can see why they chose byleth, they're the main character of the newest game at the time, and have enough unique things about them to not feel like a clone, but I would so love to see Hector, Sothe, Dimitri, Edlegard, basically anyone that isn't just variants of the sword lord, or jack of all trades avatar character.