Back on topic, thanks for clarifying Idle. If it's about design then simply look at SC3. Multiple single player game modes, things to purchase and unlock, and character customization. The last one is huge imho. The more options and details CAS allows, the more people will bring its quality up in forums and word-of-mouth, and the longer they'll play the game. It'd be best to bring the best of SC3 and SC4's options together, though this might be much more time consuming.
As far as guest and bonus characters go, an easy way to deal with it is lump them in a slot like they did for SC4. Furthermore, make them unlockable but have "core" characters (i.e. available from the start to make the seperation more apparent.
I'll bring up more later, I have irl matters to attend to lol.
Problem is, by all reliable data Soulcalibur 3 is simultaneously the worst reviewed and the poorest selling Calibur game aside from Broken Destiny. So if you're using that as a base to appeal to casuals, it's not a very good one, and it really puts a light on the discrepancy between what players SAY they want, and what they actually pay for. They say "we don't want guest characters, they don't fit into the game," but the best selling games in the series are based around guest characters. They say "we want more story modes and character customization," but Soulcalibur 3 sold way less than Soulcalibur 2, and Soulcalibur 4 cut down on that stuff even more and still outsold them. Same thing goes for clone characters
Looking at it from both points of view, from Namco's, and from the player's, there are 2 different things they want. Namco wants to sell as many copies as quickly as they can. The players want to buy a game that will be worth their money.
Namco has proven that they can slap Link or Yoda on the box and that will guarantee sales. From a business viewpoint, that's possibly ALL they have to do. Or at least all they had to do; DLC actually changes things there. Now they'll want a piece of that pie, and I don't think that has any real positives for most players. The idea of keeping people interested 3 months after the game's release only matters to the company because that way they'll have a continuing market to sell trinkets to. I'd expect way more dlc costumes and create-a-soul items in the future.
Namco can add all sorts of extra story modes and create-a-soul modes, but the only thing that's going to have a hope in hell of pulling a casual fan out of being a scrub and wanting to learn the game (aside from the rare cases of them just deciding to do it for themselves), is if the gameplay is fun, exciting, and accessible. That's the only part I care about Namco caring about. If they can luck out and make it just accessible enough that someone who cares can feel that if they could just find a resource, they could actually get good at the game, then people will look, and they'll find sites like this. Too hard, and people won't bother, too easy and they'll get bored.
That, and, I'm sad to say, online. Most people will only compete against others online. If they find the online unplayable, they won't play, or won't care to try very hard.
As for things like art, characters, music, and all that. They do breed fans, but they're even less likely to try and compete. Namco has already proven that they can do enough to satisfy that type as much as Namco cares to.