Hmm, well first who do they mean by "staff"? They can't mean the game's staff because those people would have to be pretty out of the loop for them not to know what a main fighter in the game was. Maybe Pokemon Company staff? That would make more sense, and may also help us possibly figure out what this Pokemon could be.
Anyway there are a lot of Pokemon on that list I don't know who to choose (though I think we can probably remove Pokemon who aren't fully evolved, sorry Kadabra and Scyther; only Pikachu gets special treatment... AND maybe Jigglypuff and Meowth). If I was forced to pick one I guess I'd pick... Flygon. I can see plenty of move possibilities with it, we don't have a Ground- or Dragon-type fighter yet, and it's a popular Pokemon (or was, which I think may play to its benefit).
Assuming the staff they're talking about is knowledgeable about Pokemon, my guess is their picks will mostly be popular picks (or course there will be a few favorite picks). Out of the 45 who guessed, only 1 got it right, 13 are still happy with the pick, and 31 are "salty". Now it's important to note that the 31 who are "salty" could just be mad their Pokemon didn't get picked, they didn't say they hated or liked the pick. Because of that we can't really base their response that much on the picked Pokemon though it wouldn't be out of reach if we assumed at least didn't honestly like the pick because they feel it doesn't fit. But back on point, my guess is that a lot of them probably picked a popular Pokemon: Swampert, Heracross, Kangaskhan, one of the Hitmons. However with only one person getting it right that tells me the immediate obvious choices aren't it. BUT that doesn't mean a favorite, or used to be favorite, wasn't picked. Infact I'm more willing to bet a b-squad favorite might be the Pokemon, one who might even had some attention for a little while. That gets me back to Flygon. Flygon was popular during ORAS since we all wanted it to have a Mega Evolution and for a little time after many were sour that it didn't get one, so much so GF made a statement about why (they had planned, but couldn't think of a good design). And so with that Flygon sunk back down in popularity, in people's memories but with no Mega it's hard to stand out for long. But maybe the Pokken team when picking fighters remembered this and seeing possibilities for a literal dragonfly that floats, and maybe deciding it throw it and its fans a bone for not getting a Mega Evolution, chose it. I can see one Pokemon Company staff remembering/liking Flygon past the hype, other's liking it, and people within the "salty" group having trouble seeing what fighting style it'll have and/or thinking there would be better options (like a Pokemon with a Mega Evolution).
Just to voice my thoughts on other picks I'm seeing:
Swampert: I'd like a Water-type starter, but not Swampert. We got Sceptile representing 3rd Gen starters, let's get another gen in. Feraligatr, Empoleon, Samurott, or Greninja (and Greninja seems the most likely at this point with its anime presence and it being in Smash). Also I'd imagine it would be a popular pick being a Water Starter.
Darkrai: It would be nice to have another Legendary in and Darkrai has fighting potential... but I can see one problem. If they're going to have Darkrai they'd probably also want to incorporate its gimmick somehow which I can see being a difficult thing to do. Putting your opponent to Sleep, even for a few moments, I can see breaking up the flow of the game. Now Darkrai can still operate as a frail sweeper and maybe only have its super attack having it put its opponent to sleep with Dark Void as it attacks them with Bad Dreams/Nightmare/Dream Eater, but there are other such Pokemon that can fill that role say like Latios. That said, I can see someone saying it was their pick as an oddball and they just so happened to be right.
But we shall see... and as long as it's not another Cosplay Pikachu.
