I wouldn't cut any characters, but I desperately want Sakurai to expand the umbrella of what constitutes an echo fighter and rebrand some semi-clones as echoes.
Dr. Mario, Falco, Pichu, and Young Link should be given the echo status which would free up the roster for four unique numbered fighters.
Either that or they should undergo some serious decloning, as did Wolf, Lucas, and Roy to a degree. Even Toon Link and Isabelle look and feel substantially different than Link and Villager. This way Sakurai doesnt have to renumber the four I mentioned above. Also, Sakurai needs to commit to fully decloning Ganondorf. I know he doesn't want to alienate Ganondorf mains, but it's passed due time to give this guy a more fitting moveset.
It's a rather trivial pet peeve, but having semi-clones, echoes, and alternate costumes all feels so annoying with no clearly defined rules/boundaries for which characters fit in which category.
Edit: If I absolutely had to cut characters, then I would probably cut Corrin and replace that slot with Hector or Lyn, and I would cut Toon Link in exchange for Skull Kid. I'd strongly consider making Dr. Mario an alt costume like Mario's wedding outfit, but Dr. Mario is a successful stand alone franchise so idk... I would also cut one or two Pokemon and conduct a smash poll strictly for Pokemon and add in the first and second place winners of that poll in Smash.
Surprisingly, I would keep Pichu because it represents Gen 2, and specifically baby pokemon which is pretty funny to have in a fighting game, AND is the baby Pokemon to THE mascot of the franchise. That all feels much more reasonable grounds for inclusion than what Greninja or Incineroar offer (just included as the recent generation's "cool" starter).