Honestly, it just doesn't seem... Sakurai-esc.
Even when Smash consisted solely of Nintendo characters in 64 and Melee, Sakurai's been relatively conscious about not giving any franchise too much content. Obviously, this didn't mean giving everyone the same amount of characters, stages, etc., but it did mean doing things like passing over the more popular Wario for Mewtwo and Marth to add greater franchise to Melee's roster instead of making it "Mario and Friends".
Now that we're incorporating content from all over gaming's landscape, the logic behind not wanting to give too much love to any individual series extends to the companies that are being represented as well. Of the 7 companies represented in Smash thus far, none have more than three characters, most have at least two characters in Smash, most have 2-5 franchises with representation in Smash (Namco and SNK are the exceptions to these previous two patterns, as they both have one character meant to represent their entire company), and no company has gotten more than one unique newcomer in a wave of characters.
These patterns suggest that Sakurai is trying to balance the representation each company receives so Smash is a true celebration of gaming rather than "Nintendo vs. Capcom plus friends" or "Nintendo vs. Square and some other guys are here".