Well, it's less that these designs wouldn't breach the mainstream, and more that the mainstream has changed. The people who would be off put by the outlandish anime designs are not as big of a factor as they used to. You're never going to sell persona to the "Head Up, Eyes Down" crowd, but I think the mythical mainstream has never been so accepting of weird goofy shit. These are examples of things that are generally well loved and ubiquitous in the west right now, to the point where they've gone a little outside of their original niche.
So, no, I don't think a guy wearing a masquerade mask and some red gloves really keeps it from finding some kind of success outside of the niche of anime games, especially when we do live in an era where a talking racoon from one of the most incredibly obscure comic books can be in the biggest movie release of last year.
In fact, I'd say the tone of P5 marketing has so much in similar with all of the marketing for Iron Man and a lot of Guy Ritchie films, like Sherlock Holmes and The Man from U.N.C.L.E.
It's worth noting that I myself had fears that they'd go "too anime" with P5, but I've been utterly blown away by what they've shown us so far. It really really could have been much worse, and I think the trailer has played well in many diverse crowds. I think that's why I'm invested in this debate at all, it's kind of the opposite of what I've been hearing and seeing. Goofy as it may sometimes be, I think there is a somewhat universal appeal in a masked thief living a life of passion and intrigue.
