You know, I find it amusing how in spite of the fact that there's plenty of reasons to be optimistic towards there being eight more characters not on the leaked CSS, that people tend to completely forget about it.
Actually, it took a little while for it to synch in (possibly due to the fact that people were often saying this out of mockery), but it isn't too far off that, when the roster is finished, Shulk would be meant to be paired up with the clone characters. Heck, a brilliant theory that I had was that in order to speed up the development for these characters (Dixie, Impa, Ridley, Mewtwo, and Shulk), Sakurai took existing assets from other characters and incorporated them to their movesets; they still have unique mechanics (the hair and bubble gum; a sword; permanent hover; telekinetic powers; and Monado Arts), but beyond those, they still have quite a bit in common with Diddy, Sheik, Charizard, and Lucario respectively. Shulk is the only odd duck since he doesn't borrow assets from any one character but several: Link, Marth, and Ike for sure (likely in an attempt to make him seem completely unique). For this reason, I believe the second-to-last row is reserved strictly for the eight late additions or "clone characters" if you will (and I even have an explanation for the odd numbering of the second-to-last row; the Mii Fighters take that empty slot when customizations are turned on).