Seeing all this clone discussion made me want to give my own take on the matter, hopefully you guys find it interesting.
Sakurai usually includes clones as "extras" once the rest of the roster had been decided. I have never liked this attitude, I think every clone should be planned from the start so we can properly flesh them out instead of waiting for Smash sequels to do it.
I still have nightmares of seeing Dark Pit, one of my anticipated theoretical clones (Hey, I like Pit's playstyle, and a substantial variation on it would have been pretty fun, admit it), turning out to only have 4 total gameplay differences I can literally list without having to elaborate. Whether or not you think he should have been a costume or not, if Sakurai properly fleshed out Dark Pit to, at the very least, have a Fox-Falco dynamic with regular Pit, people wouldn't be complaining and raging nearly to the same degree we all are currently. I argue people would have only been saying that Kid Icarus was overrepresented like usual, but not much else to complain about since he plays distinct enough in this scenario.
And Lucina pretty much being something as uninspired as being "Marth without a tipper" instead of something more interesting is just so sad, guys, especially since Roy was brought back with a great half-clone moveset, making Lucina look like a much less attractive choice of a Marth variation gameplay-wise.
See, some of us don't mind clones, and actually enjoy seeing variations on enjoyable or cool movesets--when they're given the proper time to be fleshed out. Even back in Melee, where we got 6 new clones, most of them were fleshed out nicely enough to feel worthy and distinct from their bases, especially in their attack trajectory and strengths. Dark Pit and Lucina don't even have THAT going for them, when it would have been easy to program since they share all attack animations save like one or two (Dark Pit even shares Pit's BONES) similar to many Melee clones' situation.
On a side note, I would have really liked to see Alph as a separate Olimar clone instead of an alternate costume for him. Olimar's moveset is so unique and interesting and there are many ways to offer an interesting variation on it that Alph would have been a great opportunity to jump on, but sadly it was not to be. Some argue it would make Olimar less unique or whatever, but again, if Alph was worked hard enough on, he would still have felt very distinct so as to mitigate whatever imaginary damage to Olimar's uniqueness Alph's inclusion would have caused.
I cannot stress this enough: All of the above situations the Smash 4 clone newcomers (and Alph) were unfavorably placed in would have been avoided had the team planned their inclusion from the start, instead of being added "after the main roster was decided." I know a lot of people groan and moan about clones in Smash, but it's important to recognize the value in them and the differences and variation they bring to the table. The more vocal we get about liking their substantial differences rather than bashing their inclusion as "wasted space," the less we'll have situations like the ones Lucina and Dark Pit were placed in, where they pretty much ARE wasted space since they bring nothing substantial to the table. It would give the Smash team a heads up to always do whatever clones they want to do PROPERLY.
(Game and Watch)
*. Also minus points for the lack of Samurai Goroh or Meowth. 
