So if an actual Stadium game is revealed it could potentially be a huge deal. If Dexit is reversed it would let Gamefreak insert as many battle slaves as they want per game. I don't think anyone gives a fuck how big the regional Pokedex is, they just don't want their Crabominable to be trapped in Pokemon Home for 5+ years. VGC is also in an awkward place as it's locked into SwSh despite being like 4 games behind at that point. But reversing Dexit for a battle simulator could be done by a relatively small team from a third party company. Imagine if the Showdown staff were hired lol.
The original Stadium / PBR games actually had sleep and freeze clause as well as a ton of other options for PVP. 3v3, 6v6, whatever the fuck you want. Add in doubles, triples if they're ambitious. Megas if they really want the community to collectively cum. Or if we're being extreme here, the option to TURN OFF THE BATTLE TIMER.
Outside the PVP aspect Stadium actually had a lot of cups to battle in. Stadium 2 even had Little Cup! Additional cups outside of standard VGC could be things like "no rules" where legends are legal, monotype cups, BST limited cups, and so on. They even had a Mewtwo battle which could be replaced by something like a Totem battle with Arceus holding the Legend Plate or w/e the new broken item is. Even generating random NPCs is relatively easy. Just pick some STABs and coverage moves. It's 4 slots to pick from a pool of moves where only like 1% is even vaguely usable. Showdown sort of does this with randbats.
Stadium also had Oak's Lab. Easy, just link to Home.
Gym Leader castle? Expand it to all gym leaders and E4 from all games. That's literally tens of hours of gameplay. They can even port the models from XY or Sun Moon directly. Legends Arceus graphically looks like a DS game, no one gives a shit!
Game Boy / Doduo / Dodrio Tower? Lets get maximum ambition here and have all DS titles released on the Switch, where they can be played at 2 or 4x speed.
Lastly we have the minigame thing. Honestly it's 2022. Just shove some minimalist generic Mario Party re-skins in and the community will collectively pee their pants. Metapod Harden gameplay literally consists of hitting A. Snore War also is just hit A. Magikarp Splash is A. Thundering Dynamo is also A... a lot. These games were so bad but it doesn't matter as long as you got a few more stars than your friend playing next to you.
Come on Gamefreak do Stadium right.