My main takeaways from Arcadion are... well, mostly gleeful incoherent screaming, this is already making a solid case for 'best normal raid series'. But in terms of actual, cohesive and verbalized thoughts, I have to divide them into two.
First of all, looks like the Arcadion's gonna be leading the post-MSQ story about the regulators--and is stanchly anti-those, but also recognizing that you're not gonna be able to overhaul society that hard on a dime. That would be like trying to revoke all cars. Or, like, the concept of currency. You're gonna need to find a better angle than that, and 'beating Alexandria's best at the thing that the regulators specifically make them good at' is a pretty solid one.
The story outside of that is sort of a stub here, but it's still a lot better than I could say about the first leg of Pandaemonium; by this point in Panda I still didn't even know what the point of the raids were beyond 'see more of this part of the world we assume you like', while there's some solid stakes and promises of the future here; we are absolutely gonna end this by fighting the President. Because if we're doing a pro wrestling storyline, it's only right to end with us fighting Vince McMahon; after all, the WWE squandered their setup for the best final boss of all time, it's only right that someone else use it.
...but I feel like, while it's not 'lore' per se, there's another very important root in this one, because the actual fights feel very steeped in fighting games.
Specifically, the bosses in this one all feel like they're lifting from Capcom fighting games. That'd feel like a reach, if we didn't already know that Yoshi-P is into Capcom fighting games specifically.
First boss is Felicia from Darkstalkers; 'catgirl with savage attacks' is admittedly sort of a given with Black Cat's aesthetic, in isolation that could be nothing, but in the context of everyone else, it tracks here.
Second boss is Q-Bee, also from Darkstalkers; Q-Bee didn't have that 'pop star' aesthetic, but a surprising amount of her kit is there otherwise. ...and honestly, 'bee lady' is actually a much rarer trope than I'd expect!
Third boss is obvious right from the opening cutscene: that's Zangief, with some Akuma mixed in. There's some actual Zangief poses in there!
And fourth boss is where things get a little fuzzier, but it might be because it's tapping into games I don't play; I can see shades of Cable and Iron Man from Marvel vs. Capcom, and I could make a flimsy case for Morrigan from Darkstalkers but only in later crossover games where they went really hard on giving her mech stuff. None of those feel like they fit as well as the first three, though; maybe the Savage tier's inevitable second form will nail things down. Or maybe it's just not fighting game stuff at all, but that sounds lame.