Let's talk Anna:
She's a merchant trickster. Been in nearly ever FE (maybe every FE?). She was all over Awakening -- playable for the first time, and her identical sisters were the merchants heralding DLC.
What could make her unique? Aside from being a redhead female, her fighting style in Awakening has a unique look to it. Like Gray Fox in Metal Gear Solid, she swings her sword handle first. When she stands, she holds her sword upright behind her. When she runs, she also keeps her blade upright behind her. Very stylish!
Where her sword is concerned, she could use the lightning-zapping Levin Sword, as seen in this official art:
She could also swing around sacks of gold and fling coins in the face of her enemies, being a merchant trickster and all. I mean, look at all of that gold!
I think she'd be great.