I wouldn't mind if more Western-dominated franchises were represented in Smash through playable characters. Of course, that's a biased as heck statement, but I have more reasoning than just wanting some of my favorite franchises in Smash.
I believe it was discussed here that one of Sakurai's goal with Smash is to introduce and represent Japanese franchises (large and small) to other parts of the world where they aren't as known. It's a really innovative idea; for example, a good chunk of Fire Emblem fans might not be fans today had Marth and Roy never been implemented into Melee. Representation of more Japanese-dominated franchises, playable or not, may seem small, but they can have long-term ripple effects that allow gamers to be more culturally endowed in facets of the industry that they may have never even thought of to explore. For me, that was Mother 3.
But what if this vision that Sakurai has was more reciprocal, using Smash Bros to introduce franchises that dominate in more Western spheres of the globe to Japanese audiences? It's easy to understand on a level of practicality why this hasn't occurred more frequently due to obvious language barriers and time needed to relay information through multiple channels (NoJ --> NoA --> 3rd party Western company --> NoA --> NoJ.) This was the format needed for Sakurai to communicate back and forth with Robin Beanland over in the UK regarding composition for the Banjo-Kazooie tracks.
If Sakurai found someway to more efficiently implement Western franchises into Smash, and he himself was on board with the idea, I think it'd be really neat to see. While we get a lot of Japan's influence, they can get some from the other side of the globe, really unifying different sectors of the gaming industry in a symbolic kinda way, while also contributing to the overarching idea of Smash being a celebration of gaming.