So what does everyone think about Smash potentially aiming to represent as many different game genres as possible as the basis for character selection and prioritizing adding characters that are seen as the face of their respective genres? So, for example, Mario is the face of platformers, Ryu is the face of fighting games and Cloud is seen as the face of JRPGs. By extension, either Master Chief or Doomslayer would be great options to serve as the face of the FPS genre. Of course, that wouldn’t be the only basis for adding characters but it could be a fun side goal when it comes to consideration.
I think their current method of choosing third-parties, whatever (apart from fan demand) prompts them in those directions, isn't broken, so probably won't be fixed. Smash has never really concerned itself with representing all genres as much as just different notable series, and I don't imagine that changes.
However, the further we get, obviously the likelier it is new genres get folded in. I would be surprised if the next game came and went without an FPS character, for instance. Not because they were trying to include an FPS character specifically, but just because they decided on Master Chief, or Doom Slayer, or whoever it may be.
And that goes for any unrepresented genre: battle royale, MOBA, hero shooter, MMO, soulslike, roguelike, music/rhythm, beat em up, horror, visual novel, etc. If we get a character from those genres, it will probably be for the character/series, not so the genre gets ticked off.
Plus, for as many new genres as could be included, never bet against JRPGs.