I guess we could just say that the issue may come from Localization troubles [A language problem in some sense too]. From what I know of the word, localization means translating messages to another language. It's a part of Game designing too.
Well, we have 8 fighters so far. Now it makes me think as to who will be the last 6 pokemon to fill up the six remaining possible spots.
After watching this person's opinion, I agree to some of them (Blaziken is already confirmed). But for me, the last 5 fighters that I imagine could become the next bill for the remaining slots:
a. Wigglytuff - Taking courtesy for us PMD fans, this guild master is a VERY tough boss to fight. And the fact that he has a godlike powered Hyper Voice in his story (courtesy of Special Episode 2 in Explorers of Sky), I say that he could represent the normal types. [Alternative: Cinccino in order to contest Pikachu and Weavile as a small ranged attacker while being aggressive in Close Quarters Combat with Tail Slap]
b. Drapion - with his size and claws, he could play the grappler type of fighter where most of his damage comes from grab damage with the rest of his attacks doing mediocre damage. Probably a good Poison Type candidate. [Alternatixe: Toxicroak]
c. Zoroark - the video link tells it to me already
d. Haxorus - the video link exactly says my opinions as to why he deserves it. [Alternative: Garchomp or Druddigon]
e. Diancie - with her debut on the movie, with the capability of turning her gems to lethal Diamond Swords, plus with her spammy attacks like Moonblast + Diamond Storm, she could be a very utility heavy pokemon with good Speed while holding a middle range height [Alternative: Aegislash]