To elaborate further on the "hierarchy" of characters within a series like we've been discussing, I'm generally pretty lenient on what that entails but I think for many series there's a clear bare minimum lineup that must be maintained. And then once that is established you can do pretty much whatever.
Like for example, we're at a point where I think anyone from Mario is viable.
are the absolute must haves and anyone after that, as far as I'm concerned, is bonus (excluding those who can represent their own series like Yoshi and Wario). Like, Rosalina isn't objectively the fifth most important Mario character but we reach a point where it's negligible and no longer much of a factor.
is another one. We can get into the weeds of whether or not Impa is technically the next most important character, or whether one-shot supporting characters ought to be playable, but the fact that it's a debate at all is telling enough.
These are extremely obvious but, for some reason, it's Street Fighter that this community often finds itself struggling to grasp. Anyone with a surface level knowledge of the series could tell you that Ryu and Chun-Li are the faces of the franchise and the absolute musts for any SF crossover (the only two SF characters with perfect attendance in Vs Capcom, both front and center on the cover of SFV...), but since we got Ken as an echo fighter it throws them for this loop where they question how important Chun-Li really is. It's unbelievable to me that people are either that detached from general knowledge of Street Fighter or that confirmation bias is just so strong in the community that Chun-Li getting snubbed for a relatively easy clone means she wouldn't be a priority.
Anyway, I think the conversation is mostly over but I do think there's some necessary order for certain series on the roster, and Ken withstanding Street Fighter is one of them.... Sonic is another story, though.
I would pick Morrigan, not because of anything about reps or whatever but I like Darkstalkers marginally more than Street Fighter and there's a lot more to gain through signal boosting a dead franchise rather than one that gets a lot of love as is. The inclusion of Morrigan in Smash would be amazing as a fan of Darkstalkers but also a beacon of hope for reinvigorated interest in the series.
I want them about equally but while I would be excited for Chun-Li, Morrigan would blow my mind as it's the furthest thing from my expectations.