Well, if we're seeing four cuts then we obviously lose Rosalina and Bowser Jr. The sticking point is if we only lose three, in which case we can go back and forth about those two and whether or not we prioritize series relevance or gameplay essence. Rosalina was historically higher priority, but I'd say ten years can make a significant difference when weighing their respective popularity or importance to Mario as a whole. So yeah, to your point that becomes a trickier situation, but that's the fun part right?
I think I'd argue this middling "limbo" of fighters is pretty clear. The major Nintendo series easily keep their major characters, the mainstay smaller series can easily maintain their protagonist. Star Fox, Mother, Kid Icarus will remain represented, their protagonists will be high priority, but may suffer a loss of a major character. Whereas series like Mario, Zelda or Kirby will maintain their established major characters and, if applicable, are in danger of losing their secondary cast. So something like Falco, Wolf, Palutena, Rosalina, Bowser Jr, Sheik... those are dwelling somewhere within that grey area. And then as we talked about the other day, that may involve series with a single character but less to offer moving forward or a lack of content in the game thus far, making them easier to cut loose without a major status quo change. Ideally we won't have to breach that limbo too deeply but the possibility is there. Outside of being on the fence about a handful of those characters though I feel like it hasn't been that difficult for me to pin down who I consider the priorities and still manage to stay somewhere in a reasonable ballpark. I dunno, just using that as a jump off point to ramble I suppose.
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Somewhat related side note, if push comes to shove and we could only keep one... would you guys keep Falco or Wolf?
I feel like Falco is the easiest answer for legacy reasons, but Ultimate Wolf is a major standout character IMO and I wouldn't mind if they let him get another crack at it instead. After all, I feel like at a certain point sticking to tradition can start limiting the series a bit creatively... I love all the Melee mainstays but the roster doesn't need to look exactly the same every game. So I think I'd personally lean Wolf, but I would like all three to return given the chance.
I feel like part of wanting to ask this is also just to shed light on how great these two are, so I'm personally viewing this more as a positive I really wanna keep this guy around vs a negative I wouldn't miss this guy... I'd miss Falco a lot. Falco and Wolf have some of the most personality in the game, and I think utilize their designs and animal types in a fun way. For Wolf in particular, it's a little surprising how few "feral" characters exist on the roster. Giving someone that really brutal up close and personal style is something that I think the roster really needs, particularly in his weight class.