This is an aside, but has "boomer" lost all meaning? Genuinely curious, Boomers are middle aged and up, and the vast majority of them are likely not on Smash forums arguing about Geno. I have no problem if they are, I'm just confused, because the Geno demographic is likely mostly millennials, who are not boomers.
THAT said, I'm going to go out on a limb and say Nintendo doesn't care how Geno fans are viewed by the community. They likely just see a lot of people talking about Geno and, if they're going by the (likely a) spreadsheet that says "Geno has been mentioned 999604023059 times on Youtube, Twitter, ect!" they're just going to say, "Hey he's Mario themed, he's popular with Smash fans, lets do it and make the fans happy!"
Or they just looked at the Ballot, which by your own admission Geno seemed to do well in. The nitty gritty they don't care about.
I just don't think some perceived notion of "baggage" is going to disqualify a character. With characters like Ridley and K.Rool gone, he's got one of the oldest and largest followings. I wouldn't count him out.
Buuuuuut I also think that Waluigi is as much or more in the running if we get a Smash reveal during a themed 35th Anniversary direct, personally. Waluigi has meme popularity, is relevant, is 1st party, would fit the 35th anniversary more, and I'm genuinely surprised hasn't been mentioned much. I highly doubt the Assist Trophy rule will last.