Considering Aelita left all her pokemons except Hawlucha and went on her own journey, i think it is possible to make her own episode, how she actually gets to the springs, figures out the mystery of the Amethyst cave and gets badges to become less useless, since that was troubling her. I think that would be great.
In terms of past backstory, i think i would like to see the perspective from Anathea and Flora. First of all, continuing the theme of the importance (somehow) of the Amethyst cave statues, i'd like to see how exactly Anathea was able to make Vitus fall in love with her. I think that would show us a lot of his sides we didnt see yet, because for now he is a straight up evil dude with horrible goals with no sympathy towards him.
As for Flora, id like to see her perspective on things as well, how she fought for badlands and against Cassandra. Also would help us humanise her a bit more.
Also we need more Elite 8 members. Karen is one of my favorite characters.