I'm supposed to happily put down extra cash just to unlock my main character and then buy the game twice across multiple platforms to have the full experience? I don't really think paid DLC fits Smash thematically, as silly as that might sound. It's supposed to be a celebration of all things Nintendo, and locking out pieces of that history from certain players just feels weird.
Your main is your main for the game you main it in, there's never been any promise your main from one game will appear in the base package of the next. The idea of paid DLC is that new content is made
post release and priced
reasonably as a way of extending and growing the base, complete game instead of having to wait for
another game to be released in order to access that content. So, in the fair world, if a character is cut from the roster it is done so for good reason. And if it is added as DLC it was made post-release and priced fairly. No game truly releases content complete. It's the artist problem: nothing is ever finished until you're forced to finish it, because creators will keep adding/changing stuff forever if left to their own devices.
That being said, all of this is subjective and I can see how it would suck to main a character that has appeared in most releases so far (like Ice Climbers) and then seen that character cut from the franchise only to be added later as priced DLC, especially if that price is unfair (something I'm not confident Nintendo has a full grasp of yet). And again, like Valve, I really think Nintendo would benefit from adopting a "free update" policy for Smash and Kart. Well, maybe that's not economically realistic as the Wii U takes, but you get my point.
Ultimately it comes down to the idea that "games as services" is a great philosophy when handled by producers/developers who have a respect for their audience. There's no reason for people to oppose the
idea of DLC yet openly welcome another fucking game years down the road that, for most part, advertises new stages and characters as a way to differentiate from the last entry. Realistically Mario Kart 8 and Smash 4 are very, very similar to their predecessors, and the appeal is we get new tracks, new visuals, and a new roster. Everything else is gravy. DLC helps circumnavigate this compartmentalised release schedule by growing the product that exists
now into something bigger and more beautiful. I adore the idea that I could buy Smash 4 this year and, in three years, still be playing it with new characters and stages that didn't exist three years prior. Same goes for Kart. These franchises would benefit tremendously from evolving content, in the same way many other fighters, shooters, and racing games do. If I'm happy to pay AU$80 for a new game a few years from now, I'll happily pay money for similarly bulk content (or drip fed over time) to grow the game that exists now.
But yeah, pricing fairness is a really big, subjective question mark that means different things for different fans, and it's easy for the audience to get "screwed" out of good content by unreasonable pricing. Amiibo is ripe for this, because locking digital content behind high priced physical objects is bullshit, but thankfully Smash doesn't seem to be going down this path (touch wood for Kart). In the end I do hope Smash sees DLC, and a lot of it. And I don't mind it priced, as long as it's fair.