I had an idea similar to this, back when I was conceiving some hypothetical roster. With the complaints about all the "Marth clones", I was thinking that, instead of just having slightly similar semiclones for different sword lords, why not appease a bunch of Fire Emblem fans at once? With the majority of the sword-wielding lords, you could place a majority of them into a single character slot as mere alternates (e.g., for Marth, you'd have Alm, Seliph, Leif, Roy, Eirika, Lucina, etc.). They'd differ in voice and appearance, maybe some animations, but not enough to even be classified as an echo fighter. The problem would arise with characters like Ike, who are popular protagonists with the same weapon yet a different style that wouldn't work in the context, just like you said.
Of course, this would sacirifice a character like Roy's uniqueness, but IMO I don't think they needed to craft this whole new moveset for him, especially when there's only a few sparse references to his character in Binding Blade. With these alternates all being one character, it'd be a good opportunity to introduce some techniques that other characters could perform as moves to make this character broad in references rather than just being character-specific (an example: Eirika's attack animation from the Sacred Stones could make for a cool new Side Special).
If an axe/lance-wielding character was developed and they got the same treatment, that'd be pretty cool. Anything for Hector.