I thought I'd mention something regarding if we have 72 characters in the roster for the Smashdown mode.
That is of course divisible by 2, 3, or 4. Though one thing of note is of course is when we saw the Smashdown roster in the direct the Mii Fighters weren't in that possibly saying they won't be a part of that mode.
"WHAT THE HECK? DOES THAT MEAN POSSIBLY ONE MORE CHARACTER TO FIT SMASHDOWN?!?!" you might be asking
Noooooot exactly for during the direct we did get an example of the roster being dwindled down
They used a four player example... and after this match there's only three characters left.
So either...
1. One player is eliminated for the next match. Most likely whoever got the least wins and/or lowest score
2. The roster restarts as a sort of final round where you can choose whoever you want in one last attempt to take the win if things are close
Or 3. Smash Down just ends when there are more players then there are fighters left.
Granted with Isabelle, and presumably Ken and Incineroar there would still be 6 more characters meaning yet another match could go down. Let's assume the same scenario happens like what happened with this example. You have Game & Watch, Olimar, ROB, Isabelle, Ken, and Incineroar as options still for the four players. Meaning only two would be left. Which would again either go to a final bout between the Top 2 with the only characters left or the game can end and/or choices restart from there. It's an interesting speculation of how this mode might work even if they have a full roster that isn't divisible by 2,3, and 4 when they add DLC. And/or if you tried Smash Down prior to unlocking every single character.