You’re opinion is controversial but understandable…that is till you mentioned Chun-Li. Now that’s just blasphemy. The big three being Ryu, Ken, and Chun should always be in a main Street Fighter game, no argument.
If we have a cast of 24, I’d love for at least 6 of them to be new. New characters are new blood. For a throwback (arguably a remake) like SF4, all the oldies being in it is good…but SF5 needs to forge ahead. It will help give the series momentum.
There are gonna be new character’s no doubt. But no need to throw away the icons like some people keep demanding. It’d be like removing Scorpion and Sub from MK.
Like when Scorpion wasn’t in MKIII? Which was an extremely popular iteration of the game?
As long as you have some mainstays, you will have the core fans. Without NEW things in considerable quantity, however, you will not pull in new players because they will glance and see a lot of “same old same old”.
16 to 18 classics from 24 characters is PLENTY. Hell, it’s more than the cast of SFII’s classics in total. Having at least a quarter of the characters be new gives an impression of a good amount of new stuff. New is exciting. New gets sales. Sales keep the series alive. Over reliance on nostalgia kills.
Hey he’s not naked 
UMK3 was the extremely popular iteration of MK, and it had Scorpion. Looking at their recent entries, MK finally figured out after many trials and errors the right balance of old and new.
I think a cast of 24 with 6 new characters is a very fair and generous arrangement by the way. IMO this is how I would do it.
6 Series Mainstays (Ryu, Ken, Chun Li, Guile (or Charlie), Bison, Sagat/Akuma) - These are the characters that should be and/or are very likely to be in every SF game henceforth and have attained iconic status among most everyone, they are practically synonymous with the name Street Fighter more than any other character.
6 Popular Classics of their respective games (Karin, Alex, Sakura, Cammy, Urien, Gief, Vega, Juri, etc.) - These are the characters that have large fanbases in the community and are likely to be in a SF game.
6 Wildcards (Oro, Q, Birdie, Adon, Guy, Necro, Gouken, Hugo, etc.) - These are the characters that do not have as big a fanbase but are conceptually good (possibly better than characters in the previous categories) and appear in SF games more unpredictably
6 New Challengers - There must always be room for new blood. It is the SF way. 25% is a good percentage. I would say more but the game should also be an opportunity for old characters to become new, so reinventing old characters is kinda like have new characters, kinda.
1 Final Boss - Preferably a new character or someone who has never been the boss in a numbered entry in the series.
I think it is VERY important for all returning characters to evolve and adapt to change. Some element of risk will have to be undertaken to keep things fresh. So far SFV has achieved this IMO and is on the right path.
I also believe that fondness can make the heart grow fonder and that familiarity breeds contempt. Same thing happens with characters. Cycling characters in and out, depending on the needs of the game, is a great way to keep from over-saturating people with the same things again and again.
For instance, I don’t need Vega in a game. He is undoubtedly my favorite SF character…but I didn’t freak out when he wasn’t in Alpha. Nope, I just picked up a new character (my boy ADON!!!) and went from there. Similarly, when a bunch of characters were dumped for 3, I learned to really like Urien (along with some others). When we cycled into SF4 and, lo and behold, no Adon…I started playing as the new guy Seth (and Rufus and back to Vega). BAM! SSF4 hits and Adon is back bay-bee! Wooo!
Which is why I hope Urien is in the new game. I want to play as him again in a current game.
I’m honestly more interested in new characters though…or re-imaginings and updates. I want to find new characters to enjoy and I know I can always go back to previous games to play previous characters.
As said, 25% seems like a great number. I really enjoy the influx of new characters in MKX and though I lost Smoke and Rain (my mains) from MK9, I’ve EAGERLY adopted Erron Black as my new fav MK character EVER to play as.
I hope the next reveal is a new character. We’ve seen Ryu, Chun-Li, Bison, Charlie, Cammy and Birdie (woo!)…we’re overdue for the reveal of a new challenger. Heck, really shake things up and reveal a PAIR of new challengers like the pairs we’ve had revealed so far. Then show off some more oldies…then 2 more newbies…then more oldies…then 2 more newbies. 6 / 2 / 6 / 2 / 6 / 2. BAM! 18 old, 6 new.
People raged hard at MKIII for missing characters like Scorpion and what not. Ultimate MK3 which included Scorpion and other omitted characters was the fan favorite. And I did not say not to have new characters. I simply said not to do away with the icons. A lot of casual players have this, “out with the old in with the new” attitude and I don’t like it. Yes we need new characters to draw in new players, But we need our icons to maintain the core fan base and to keep up the tradition. if a game where to just drop the old characters and insert a fresh new roster ever game, well just look at COD. After Modern Warfare series, it was a new protagonist each game and the old ones where just gone. Like how is anyone suppose to get attached or invested in anything if characters just keep getting the boot?
It took me literally YEARS to get over the loss of Dictator, Claw, and Boxer in SF3, totally and intentionally snubbed it. Offended by Capcom for not including them would be an appropriate description of my state of mind then. But during the drought in the early 2000s I found 3S and then I found Urien. Finally, a new villain worthy of my affections and if it weren’t for him I would’ve never gotten into SF3 (or other characters like Q, Necro, Alex, etc) in the first place. So I really want Urien in (and Gill dead). Once CvS2 was in full swing, it didn’t take me long to migrate to it, because it did have my absolute favorite characters.
MK has a bigger variety of villainous characters so I will always find a favorite of mine in a game. It was never an issue in the MK series to find a character I like.
But my point is, not having a favorite in the game or anyone who can fill the void (personality wise and gameplay wise) really can put you off a game. Most recently during E3, Maximilian Dood commented on how he couldn’t enjoy playing any of the current SFV roster because he couldn’t find a character he likes or relates to (he really likes Ken) and important it was for SFV to get the characters right. There are many people casuals and hardcore fans like him who simply will not pick up a game if the initial roster is not attractive to them, and will wait it out and see if someone they like gets added.
Sakuras story is, she just wants to get fucked by Ryu. Ya thats a really interesting character. At least Chun’s father was killed by Bison, and still has time for getting fucked by Guile
CoD is a bad example. How many people actually play CoD for the campaign? And for the people that do the characters the player controls become mimes. All the character gets sucked right out once the player is in control.
CoD has a story?!?!?!
Juri:
V skill: ???
V-trigger: Feng Shui Engine, movement increased by 50%, all moves become cancelable into anything (save throws and they can only be canceled into once, meaning you can’t spam cr.mp xx fuhajin store loop etc etc). Kinda like How it works in 4 but more powerful and more flexible. They can also be canceled into any button strength regardless of what was used first.
V-reversal: Kasatushi is able to counter anything and can be canceled at any time (even during dodge phase EXCEPT when passing through an opponent or object)
Had to edit some things because it didn’t make sense. Not sure what her V skill could be though…Not a clue.
Hmmmmmmmmm If I had to guess (still butthurt about birdie making it in but I guess that means rufus is a no show then?) then…Akuma and…Q or some new character.
Perhaps Vega 
I like how you think
OK COD was a bad example. But it’s the first game that came to mind when I think of a series that constantly rotates characters. But the point is that you have to have your shall I say “foundation” characters. The characters that have become so engrained into the series that when you see the characters, most gamers would know what series it is. When gamers see Ryu and Chun they already know it’s Street Fighter.
Which is why I agree about keeping them
Some guy’s gonna do something terrorist-like! Time go go all “Murica, fuck yeah!” and shoot the shit out of them with bullets and explosives out the ass!
For me, the V-trigger system is making certain characters I never play, like Chun, or characters I played around with, like Cammy n Birdie, much more interesting so I would definitely now give them a go. So, I don’t mind some of the old blood being in the game as long as their SFV versions are appealing.
Also, less shoto the better IMO. I’d be cool if Akuma didn’t make the cut. Ken’s kicks are too cool so he should be in it. And maybe give the legacy shotos a go like Sean n Sakura (definitely an older Sakura).