Had an idea. Not saying it's a good idea but an idea it is nonetheless. It goes something like this.
Instead of everyone arguing over what should and shouldn't be in every single game why not make a separate Soul Calibur or at least Soul Calibur style game devoted solely to guest characters. Throw in the CAS silliness too and bring back custom movesets.
Let Soul Calibur proper go back to the pure arcade style fighting game it was always meant to be and let people who want to argue about custom character hitboxes and what guest character belongs in what fictional setting do it somewhere else so the hardcore players can go back to just arguing about such classics as 'OP' characters, tier lists, frames and bad matchups among themselves just as God intended.
Also incidentally no more cutting off parts of the roster behind a paywall so the fanbase is essentially divided and may as well be playing completely different games. You could indeed dump all that trashy nonsense into this 'guest character' mash-up/spin-off/whatever game where it might even be sensible to presume different characters will appeal to different people and fanbases and frankly I imagine no one will particularly care if they're missing out on parts of the game they were never particularly interested in to begin with.
Well that's it... Remember. I never said it was a good idea.
I don't see how this would be workable for the developer/publisher or beneficial to any players/consumers. Just because people have the willingness and enthusiasm to bitch and moan about something does not mean that it actually qualifies as a real, legitimate, and serious problem that has to be (and can be) solved, especially when it comes to the whiniest, most entitled, and crybaby/crybully elments of the fandom. Let's break this down bit by bit.
First, in principle, I don't think the idea of an all-stars fighter game is necessarily a bad idea, as a concept. I mean, Smash Bros. demonstrates pretty conclusively just how big a draw such mash-ups can be. But you have to remember that Nintendo is ideally set up to produce such a game, since it has the largest games IP portfolio in the world. The cost and complexity of negotiating and licensing a full roster for a Namco-produced game utilizing Soulcalibur's engine would be completely prohibitive, especially if you wanted mostly characters from Triple-A titles. And not just the asking price for the characters to appear, but then the actual process and expense of the IP management and licensing processes themselves. To say nothing of the time necessary to adapt a character faithfully and in a manner which is balanced and works within a SC game's mechanics; there's a reason there's never been more than three guest characters in any previous game.
None of that makes good business sense for the parties involved. A few well known guests make for a little bit of buzz for a game that's already largely going to sink or swim on its own merits (but could use a a small sales boost for the base product and each season pass. An entire game made of guest characters, by comparison, is a gimmick that's only go to appeal to a limited slice of any already relatively small FGC. Meanwhile you lose any committed fan base of an established FG franchise. And if you don't have the kind of community-cultural connective tissue to make this product a better cost-benefit bet, like Nintendo does, the risk of it selling a mediocre number of copies does a lot to de-incentivize the expense. Not even Sony was able to make this concept work, with its huge ability to leverage characters in utilizing its business relationships with one out of every two developers in existence.
Let Soul Calibur proper go back to the pure arcade style fighting game it was always meant to be and let people who want to argue about custom character hitboxes and what guest character belongs in what fictional setting do it somewhere else so the hardcore players can go back to just arguing about such classics as 'OP' characters, tier lists, frames and bad matchups among themselves just as God intended.
The thing is, why should we give a f@&% if a bunch of lore nerds have a bunch of incredibly silly arguments about who should or should not exist in this most thematically cornball of all game franchises? Seriously, even if they stop having these debates among themselves and bring them into common community spaces like this one? How is that really hurting anyone? I mean, the worst that has ever happened to me as "fallout" from such activity is that I couldn't resist pointing out how ludicrous it is to get bent up over the continuity of such a goofy story. And yeah, that's happened about a dozen times over the years, but nobody put a gun to my head to point out that serious narrative criticism is probably best reserved for non-cornball stories that don't have characters that are simmultaneously a ninja, a demon, a samurai, and a (wooden) cyborg . And frankly the little nerdlings have always been more or less polite about the criticism, in a "we'll have to agree to disagree" sort of way. Regardless. I don't know anyone beyond a certain scrubby threshold who actually wastes their time arguing about such.
As for hitboxes, people will be creating needless drama (and occasionally have legitimate complaints) over that topic regardless of whether or not guests exist; it's a product of design, not thematics. And I'm not entirely sure how you are defining a "pure arcade style fighting game", but I don't see how the more recent mainline entries in the series are any more or less that than are the older ones--other than the fact that the games don't appear in actual physical arcades anymore, and that is also a business decision that is entirely independent of guest characters.
Also incidentally no more cutting off parts of the roster behind a paywall so the fanbase is essentially divided and may as well be playing completely different games. You could indeed dump all that trashy nonsense into this 'guest character' mash-up/spin-off/whatever game where it might even be sensible to presume different characters will appeal to different people and fanbases and frankly I imagine no one will particularly care if they're missing out on parts of the game they were never particularly interested in to begin with.
I know this complaint is made in good faith, but honestly, this whole "I want everything at once at the beginning" mentality is unrealistic in the current industry, counter-intuitive to everyone's needs (and the best way to deliver them), and not in the consumer's favor. The costs for producing these games has gone up by truly exponential ratios over the last two decades. Meanwhile, this genre has an increasingly smaller chunk of the overall consumer space and the install-base for particular platforms. There's no way they can give you a game like SCVI, inclusive of all its DLC, for less than $90, if they want to turn a profit. Meanwhile, the standard cost of a full-price game has been frozen over the same period at $60--and the reality of the situation today is that you can only maintain that price for the first few months, before your asking price has to fall precipitously to maintain sales. The combination of these factors means that if Namco (or any developer) were to follow your demands and not do any continuing-support/DLC content to recoup some extra profit, they literally could never make a Soulcalibur game again and actually expect it to be profitable. Meaning the series would be dead.
People need to get over this arbitrary, currently largely knee-jerk and entitled opposition to longform game release schedules allowing the companies to make a little more profit on delivering a full roster. The developers and publishers have to make money, or we won't get these games. Or the games we do get will be piddly in terms of rosters and content, and no one will play them, and the series will flounder and die that way. Season passes are here to stay. We have to live with it. Continuing to fight the economic reality (that these companies are stuck with as much as we are) only hurts the titles we love by maintaining unrealistic expectations that damage the viability of the product just because of the manner in which a given amount of content is sold. Some DLC is worth the extra money, some isn't, and you can decide for yourself where to draw the line. Point being, season passes give people the option to opt out at a certain price. That's actually pretty much to the consumer's benefit, really, once you arrive at a certain price point for the total package.
Well that's it... Remember. I never said it was a good idea.
Fair enough! ;)