Sakurai on why he included Robin and Lucina for Smash

We've just announced two new characters who will be joining the fray in the upcoming Super Smash Bros. for 3DS and Wii U. One is Robin, the avatar from Fire Emblem: Awakening, and the other is Lucina, a swordswoman who plays an important role in the same title. I'll skip over the details.
"What? Not Chrom!?" I suspect a lot of you will ask. Of course, Chrom is quite popular, being the protagonist of FE:A and all. However, I chose Robin and Lucina, and I will elaborate on my reasoning.
Robin appears in the game as a Tactician and functions much like a Mystic Knight (note: FF terminology, but equivalent to magic swordsman). I thought to utilize his all-around nature by assigning swordplay to his Smash attacks and magic tomes to his special attacks--that is, allow him to use magic.
His neutral special is thunder magic that grows stronger the larger you charge it. He uses fire magic for his side special, and wind magic for recovery as his up special. Although Robin doesn't use dark magic in FE:A, I decided to assign it as his down special. It isn't the first time I've given moves to a character that they don't use in their respective game in order to capture certain aspects of the original title.
I also implemented the system used in FE:A, in which tomes break after overuse. Likewise, I included a similar system for the Levin Sword, which breaks after a certain number of uses. However, both the tomes and the Levin Sword will quickly regenerate after a set period of time.
Lucina uses the same techniques as Marth, a fighter with whom I'm sure most of you are already familiar. I even went so far as to make their strength, speed, and special attacks almost identical.
However, what sets Lucina apart is the fact that the strength of her attacks is uniform along the blade. Marth's playstyle emulates the elegant swordplay of a fencer by dealing more damage when he strikes with the tip of his blade, but the damage Lucina deals is evened out. Thus, I think that Lucina will be much easier than Marth for novice players to play with.
I played all the way through FE:A and really wanted to include a character from that rich cast in Smash Bros. Naturally, I considered adding Chrom to the roster, but the decision wasn't easy by any means.
At the end of the day, Chrom would just end up being another plain-old sword-wielder like Marth and Ike. Compared with other characters, he lacks any unique characteristics.
Conversely, when the idea of including Robin came to mind, conceiving the character was so easy that I immediately saw how it would work. From standards to specials, grabs to throws, all aspects of his moveset just fell into place. Not only did he possess characteristics unlike other fighters, but he also captured the essence of the Fire Emblem series. It was perfect!
In the end, if a game isn't fun, then there's no point. Of course, it would be really easy to make a game by churning out a ton of similar characters, but that's not how I produce games.
Initially, I had considered including Lucina as one of Marth's alternate costumes. After all, she has a close relationship with him in FE:A. In such cases, even if two characters' names and voices differ, as long as they function the same way, I assign them as alternate costumes. The Wii Fit Trainers, Villagers, and Robin are examples of this setup.
However, even though Lucina shares her physical stats and techniques with Marth, the characteristics of their attacks differ. When two such similar characters function in an even slightly different manner, I give them a separate spot on the roster since that will affect battle records and whatnot. In that sense, you could say she was very lucky to join the fray!