I think Clones will be a permanent part of Smash Bros from now on. You might be thinking why and I'll explain it. As you put more and more characters into the roster, it becomes harder and harder to keep every last character well balanced with eachother. It isn't as hard to balance all of the characters with eachother if some of them are clones. You would know more or less that they will be about equal in capability lowering the amount of time necessary for balancing purposes. So I think we have Lucina now because we are close to hitting the limit in terms of balancing time available for unique characters. It takes exponentially more time to balance the game, the more unique characters there are. Expect the quantity of clones only to increase.