To be fair, a lot of that came from people being way off the mark and looking at the wrong things.
Remember how many people assumed Toon Link would be gone from Smash 4's roster, or be "replaced" by a newer Link? Turned out he stuck around, because unlike what they thought, he wasn't ever meant to just be lip service to a recent-at-the-time Zelda game. But since it felt like Toon Link was meant to be a flavor of the month, the idea stuck despite evidence that Brawl's roster wasn't chosen that way.
Remember how a decent handful of people expected Mewtwo to "take his slot back" from Lucario? That entire line of thought turned out to be wrong, but it was because Lucario never "replaced" Mewtwo in the first place--he was planned for Brawl, fell short of the final roster, and we had known that for a long time. But since their neutral specials are similar, the idea stuck despite all the concrete evidence that it wasn't true.
It's one of several problems in the Smash community: people tend to stick to whatever they already think is true instead of trying to actually understand the design team's thought processes and what they might be looking for.
That's quite easy to say in retrospect, and while I agree some stuff did seem fallacious from the get-go, like the notion that Lucario replaced Mewtwo, trends and mentality don't always become clear until after the fact. There are a plethora of characters that were added (or cut) to the roster that prior to all this, even the most rational and knowledgeable speculators would've dismissed. Or at least not anticipated to any serious degree.
For instance, people were not entirely sold on Toon Link returning because a) I don't believe the "child Link is a necessity" comment was a thing at the time, b) because he was a low priority addition to Brawl (which really does undercut how much of a "necessity" the second Link really is - seems like only in Smash 4 was child Link actually a priority) and c) there was precedent of the last-minute Link clone not making it back. Looking back, sure it seems like a no-brainer now, but given what we were working with then... I believe many (but certainly not all) of the ideologies of the time were understandable.
People are going to make totally rational errors in predicting the roster going forward as well. Right now people will argue for pretty much any character on the roster sticking around, but obviously they're not all going to. Including the unique ones.
If an ARMS character gets in it's most likely just going to be a template character with different variations, like Bowser Jr. and the Koopalings.
I'm thinking it'll be Spring Man/Ribbon Girl/Min Min/Ninjara/Kid Cobra, mainly because those five seem like they would share an animation rig easier. I don't think Twintelle or Master Mummy would be selectable in this template since they would require different animations due to their body types.
I dunno why people seem so enamoured with this idea. It's really selling all the characters short cramming them into a single slot. Just because they all have extending arms doesn't mean that's the extent of their uniqueness.
It's like getting Ryu, Ken, Akuma, Sakura, Dan, etc. all under the same slot. Or like Marth, Ike, Roy, Eliwood, Chrom, Lucina, Sigurd, Seliph, Leaf etc.
I get Ribbon Girl or something as an alt, but I don't get the rush in filling the spot with as many characters as possible, it's not a Koopaling deal where they come in a set of seven. Just have patience and more ARMS characters could be added in the future...
Please more square enix characters
I agree.
I also get the feeling SE is a bit more austere in lending out their characters, with a budget that reflects that. Especially when it's not largely for promotional purposes.