Altais
Smash Champion
Before Lucina and Robin were revealed, that same argument was made about Chrom. Even if they gave Chrom a whole different moveset, in the end he would just be another generic biped swordsmen, which I personally think we have enough of as is. [Shrugs] But that's just mine opinion....You do realize there is more to swordplay than just swinging it around right? Anybody in Smash could have a unique movement granted Sakurai and his team put work into it. It makes no sense for the Kamuis to be alternatives for Lucina and Marth when they could be their own character. Have you seen Kamui's gameplay in the Nintendo directs saw far? It's pretty clear that their swordplay is different from Marth and Lucina so I have no idea where your assumption of being "simple sword users" comes from? Their stance is even different.
In fact, I can see Kamui almost like an aerial fighter or a middle ground between Marth and Ike.
[Shrugs] At any rate, now that I've remembered that Kamui is a Manakete, I can definitely see how he/she can be unique. Kamui's playstyle could function similarly to the Laguz in Ike's games, in that you could transform into a powerful beast whenever you wanted, but there would be a transformation gauge that would eventually run out. Said gauge could slowly refill whilst Kamui is in humanoid form.