>>45824721There's a difference between a mature game that tackles serious questions, and edgy "lmao throw them in the lava" stories.
As for how I'd do things, I'd want to focus on fair but passably challenging gameplay before story. Not because I don't think story matters, but because I feel like that's not really the focus on most Pokemon games at this point. We had some attempts but it never seems to stick. In turn I think that may actually add investment and tension to the story if handled correctly; if the game is too easy it's easier to fall into a "well why would I care if I'm just going to always win anyways?" type of mindset.
Then I'd try to focus on setting, theme, major characters, and what kind of story I want to tell. This seems like it'd be some basic shit but a huge chunk of Pokemon games seem to forget at least a few of those things.
As for the broad strokes of a story I'd really like to focus on two things. Intrigue/mystery and opposing ideals. The first feels like it really suits Pokemon well, because you can have bits of lore and side content hidden away in locations that aren't on the main path, have a bit of a Cinnabar Lab scenario if you want. Reward exploration in an indirect way. As for themes, I really think this is where the rival system most Pokemon games have attempted is severely underutilized. A story about two friends who over the story branch out and come to their own conclusions about how the world works, only to end it with a big clash at the finale, feels perfectly suited to the rival system Pokemon's had forever. Maybe it's a bit shounen but it just feels suited to the type of game we've had since the beginning.