I don't want the entire pavilion be converted for the ride, as it would most likely ruin the whole aesthetic of the Pavilion and of the identity of World Showcase itself, which is to showcase the cultures of entire countries around the globe. Anime is one part of Japanese culture, but it shouldn't subsume everything else.
Could Disney just repurpose the abandoned Meet the World building and further expand it for the Great Anime Ride?
Having DCA in Japan would be kinda wild but I actually think it would work in this context, since Disney is likely to use designs similar to the original, more ambitious concept of DCA. Alternatively, Disney could also expand DCA into Disney's American Adventure where they display lands from all across America from Route 66, Texas, the South, the Midwest, New York, New England, and etc. if they wanted to simulate the true American experience to the Japanese.
For the Japanese Adventure park, it does sound like an interesting idea, if only to provide a fantasy Japanese castle be the counterpart to the Western-styled Sleeping Beauty Castle. Maybe it will mirror Disneyland in terms of land theming (Main Street USA, Tomorrowland, Fantasyland, etc.), but perhaps it doesn't have to be that way, as I do like to be surprised with whatever content is posted in this TL.