I would like to see how it generates late-80s/early-90s style features. The current pool of anime art styles are very generic (aside stylistic outliers) and I'd love to see Cowboy Bebop/Akira/Bubblegum Crisis type character designs
In many ways Miyazaki's style is "nonstandard" for anime, possibly because he was partly inspired by European artists (think Moebius, whose influences can be seen in Nausicaa for example).
I'd be curious if such a GAN could actually beat Oda at generating new One Piece characters. 20 years into it he just doesn't seem to stop at creating hilarious characters.