Hmm...I've been forgetting Mii Fighters in my analysis of the CSS. Do we know for sure how many slots they'll take?
Possibilities:
1) MII FIGHTER IS SET UP BEFOREHAND SOMEHOW AND IS NOT ON THE CSS AT ALL
a-Roster is final anyways and that's that.
b-Roster still has five more spaces to fill, with ICs, Lucas, Wolf, and either a Pokemon or Star Fox rep evening things out nicely. One more newcomer fills the screen.
2) MII FIGHTER TAKES A SINGLE SPOT
a-Regardless of whether they're next to Shulk or they fill out the second to last row, the CSS is still evened out and that's the final roster.
b-See 1b, only Mii Fighter is the final space.
3) MII FIGHTER TAKES UP 3 SLOTS WHEN ENABLED, 1 FOR EACH CLASS
a- They'd only fit together on the bottom row, which would still leave the roster even in shape and that could be all there is.
b- If there's more characters, there's only room for two more. Unless I've made a mistake (I'm in a rush now, so I probably have) Lucas would the only supposed cut character that could slot in nicely along with another newcomer, or there could simply be 2 newcomers without Lucas.
I'm sure there's other possibilities and I might have made a mistake somewhere, but looking at these options I'm obviously hoping for '1b', though '2b' is more likely. It's a bummer that the screen evens out no matter how Mii Fighters are implemented, so all of the 'a' options are more than possible.