To me “fan rules” are just created by people who have a wanted character that doesn’t fall into a specific category like spirit or AT that want to convince themselves said character is more likely.
Not necessarily, there’s some logic behind it. Fans understandably get upset when one of their favorite characters becomes an AT or spirit, since it means they aren’t playable.
But it seems like Sakurai still thinks those are valuable roles. I really doubt he’d choose fan favorite characters like Isaac & Shadow to be ATs if he thought they were “lesser” roles in the game. I think he’s happy with their representation as long as it effects gameplay. Someone brought this up for Zelda’s representation & how it’s largely stages/items, it makes sense to me.
I’m not biased either. Jill, Leon, Shovel Knight, Waluigi & Dixie are some of my most wanted characters.
I do think base game spirits are back on the table though. Atleast until we know who the Arms character is. The 4 Arms characters who are spirits are the most popular/famous characters, so if they choose someone else then I don’t think we’ll see any other spirit upgrades.