It's so adorable when people try to argue that Lucina (a character who is essentially a female counterpart of Marth.) would implement different stances. Like they try to argue with Chrom. Completely ignoring the fact that the character is almost identical to Marth and capable of doing everything he does, exactly as he does it.
I'm sure a character that would be added for the sake of being a stance character
would be a stance character. Much like how Ganondorf, a character added for the sake of being a Captain Falcon clone
was a Captain Falcon clone.
Did you know Leif can perform magic? Yeah, didn't see him in Melee in Brawl. It's because Sakurai really doesn't care what differences you have when you are so similar. So long as you can perform all the character's abilities, there is no reason for you not to. And I think the same really applies for Krystal. Not to mention it'd be kind of weird implementing her staff (which appeared once in a RareWare game) whilst maintaining her (more recognizable) pilot outfit scheme.
If Sakurai was looking for a Marth clone, the better decision was Roy. Because the existing fire effects made Roy's attacks appear much more differently than the existing magic effects if Leif was the chosen clone. They were not interested in adding a unique character from the Fire Emblem franchise, so a character utilizing magic (like Leif) wasn't in their best interest if he couldn't play the part and still seem different enough.
If Krystal was decided to be a staff user, she would use her staff. If she was decided to be another variation of Fox, should would probably play like Fox. It all really depends on how Sakurai and the development team want each character to play.
I've also heard people argue that Dark Pit would use different weaponry. Yeah, a palette swap of Pit being the first clone exemption. Seems legit.
If they wanted Dark Pit to use a variety of weapons, sure. If they weren't interested in making Dark Pit anymore than a color palette, he would be a color palette.
Personally I hate Chrom. I don't know why, but when I played Fire Emblem Awakening he was soooo boring.
And potential wise, I don't think Sakurai is even going to CONSIDER him.
I may not like Generic Blue-Haired Swordsman either, but saying Sakurai isn't going to consider the poster boy for the game that saved the franchise is kind of a bone-headed thing to say.
If he asks Intelligent Systems who they would recommend as a new character (which he has done with Roy and Ike IIRC), it would probably be Chrom or Lucina.
How they play and what makes them different is all to Sakurai's interpretation, not yours. It's the exact same thing as he did with Villager, Mega Man, Wii Fit Trainer, Rosalina & Luma, and Little Mac.