I think Animal Crossing works so well as a theme park property because the player is the main character of their village life just as the guest is the main character of their theme park adventure. Animal Crossing caters to a much different audience than a typical video game because of its slower pace and open ended story telling and would similarly appeal to an audience that’s less represented in the park.
I think Animal Crossing would offer something fundamentally different to anything else Universal currently offers, or is being discussed/speculated. LOTR, Zelda, Wicked, etc - all fantasy adventure stories which are all exciting and unique in their own ways but the genre already has representation in the parks.
From a logistics perspective I could imagine designing an Animal Crossing area to be a huge people eater with a high capacity dark ride (its a small world style tour of an Animal Crossing village, a story outline like bdubs described could work well ) show based attractions (Country Bear Jamboree meets KK Slider live), flat rides, meet and greets with Tom Nook and other villagers, shopping and dining.
From a business perspective, I think AC would move a lot of merch. It has that same kind of kawaii aesthetic that Pokémon has that appeals to people who are familiar with the game and people who just like cute things. Anecdotally, walking through Target I see a lot more Animal Crossing merch (lego sets, apparel, more) than I do Zelda (the occasional Hyrule shirt).
I think it just represents something that Universal doesn’t really have and could benefit from.
Also including this quote of a post I made ages ago arguing for the strength of the brand: