New Stadium

Of all the reason why I think a new Stadium game could be amazing, one of the most compelling to me is that it's the perfect answer to an all regions game.

Since Gen 3 I've known so many people bring up all the time how good an all regions Pokemon game would be. But anyone who's familiar with the discussion knows all the problems with it as well, the levelling being the main one. Stadium solves this entirely, as you aren't gaining experiences as you play, the level caps remain static.

I also just think there's so much you could do with a Stadium game like this. Not to mention content. I imagine it something like this:

Imagine instead of the "Round 1" and "Round 2" system, it's based on region. You could have it start you in Kanto/newest region or you get to choose where you start, either work. Inside:
Individual Gym Leader Castle for each region.
Individual cups for each region.
So say in Kanto you have Poke Cup, Pika Cup, Petit Cup. In Johto you have Prime Cup, Challenge Cup, Little Cup. In Hoenn you could have Doubles Cup, Monotype Cup, Palace Cup, etc (except please don't actually do the Palace Cup).
Then after clearing them all you unlock Round 2 and do it again =) (after you unlock a Champions Cup ala PWT!!)

And of course, regional minigames! Different minigames with pokes from that region! Ahh!

There's a bunch of different ways you could interact with rentals:
Being able to unlock certain held items after clearing certain stages. The obvious one would be getting Z crystals when beating Alola "leaders", so I think putting in other items for other leaders would work to mirror that (e.g. type boosting like Mystic Water for beating Misty)
Specific move tutors for clearing Cups - something like if you beat say Prime Cup you can teach one rental Body Slam over one of its moves. There's a bunch of different ways you could implement this, but you'd have to be really careful to balance it, as if the move(s) were too good or too accessible it'd be way too powerful a system, but being able to change what mons were good as you played would be really rewarding too.

You could obviously use your own Pokes for all this...and then online battles with all these different cup rulesets too! And minigames! Unfiltered ramblings but this sounds sick pls make will buy.