While the 14x4 thing had been discussed before, the method for getting there is kind of flawed.
Yes, Brawl's CSS slots were resized when more characters were unlocked and it is possible that Smash Wii U's can do the same.
However, your comparison goes by a
near-complete roster for Brawl (with only Wolf missing) where the icons are
smaller to a roster of only 14 plus Random.
The icons change both height and width the more characters are present and how many are in the same row, especially evident when hacks are involved to have only few characters/slots:
or more than the final amount in-game:
(Note: This is 50, the
maximum Brawl can hold on the CSS.)
With this being the maximum height/width of a slot:
So I guess the point I'm making here is, the
concept you're making is good, but not the means to
get to it.
And now that I've done this research, I now raise a new point (not specific to you): Don't go by how many slots can "fit" no matter what. Brawl can hold 50 of them yet it doesn't even come close to that number.