I also see Chrom being playable. It's not just that he's unique, he's also Fire Emblems "Recent Shining Star" of late.
Here's my theory. As far as Fire Emblem goes, Sakurai adds in Marth and the Recent Shining Star of the time. Roy was that Recent Shining Star at the time of Melee, but Ike at the time of Brawl, now it's Chrom.
But now that Chrom is stealing Ike's thunder lately, I'm worried about Ike getting cut, he was one of my best characters. I'm not saying we can't have Ike and Chrom too, it's just not likely considering that Sakurai cut Roy from Brawl.
I don't think that's necessary. Roy was planned to be with Ike and Marth, but he was cut because they didn't have the time.
Not to mention that Ike grew into an icon for Fire Emblem. He's still a big deal to the series in general. He was also one of the most popular newcomers to Smash, so I think it's a common idea that Smash wouldn't be as good without him.
From what I said earlier, I'm not saying that Chrom is the be all end all most unique choice, but common sense dictates that the most iconic character from a game would always be considered. Robin is nowhere to be seen in most advertisements from what I've seen. You have to admit that he would make a whole lot of sense, and it's not like it's impossible for Chrom to be unique.
Plus, if you want to get into specifics, those of you who argue, "Not another swordsman!" That's what we would have had in Brawl. 3 guys with swords. Yup.
There was something else I wanted to say, but I can't remember what it was.
EDIT: Oh yes. I remember now.
Basically, Chrom is too much like Ike? Ike was originally fast and strong in Path of Radiance. In Brawl, he was slow and strong. They altered him in Smash for who knows why..maybe Sakurai wanted to make him as different from Marth as possible and fit him into a specific niche? I mean I'm not being a **** here, I just honestly feel like that was it. I could be wrong.
Anyway, my point is, is that Sakurai isn't afraid to mess with source material to make a character work. So I don't see why there is so much fear for Chrom getting in when it's a very likely scenario.