Okay, call me crazy (many of you do anyways) but I just realized something by re-reading my last post. The third party franchises that got Mii costumes in Smash 4 were:
SEGA: Sonic, Virtua Fighter
Capcom: Megaman, Monster Hunter
Square: Final Fantasy, Mario RPG
Namco: Tekken, Tales, Tower of Duraga
Sonic, Virtua Fighter, Megaman, and Monster Hunter all got promotions in Ultimate. Knuckles, Akira, Zero, and Rathalos all became assist trophies. What do these assist trophies have in common? Their associated Mii costumes came in pairs.
Tails and Knuckles
X, Exe, Zero, and Protoman
Rathalos and Monster Hunter
Akira and Jacky
The leftover third party Mii costumes didn't. Chocobo is a hat, not a Mii costume, so Geno was technically the only Square Enix costume in Smash 4. Heihachi, Gil, and Lloyd all came in seperate waves in Smash 4. Neither Square or Namco has yet to get any kind of promotion. Obviously there's not going to be new assist trophies so for Namco that basically leaves Lloyd or Gil and for Square literally just Geno.
Something to note too is that, like Heihachi, Gil is actually part of Pac-Man's taunt:
Namco Roulette is Pac-Man's up taunt.
www.ssbwiki.com
This was once discarded as a minor detail but, then again, look what ultimately ended up happening with Heihachi.