I want them to tackle a medieval style Unova. For a region based on New York, it sure has a lot of ancient ruins and castles.
Not to mention Unova’s lore and history lends itself to the medieval theme. The Twin Heroes? The Fire that consumed the region from which the Sword of Justice rose to defend? Dragonspiral Tower? Desert Resort? Abyssal Ruins? Moor of Iccirus?
They could totally have a group that inspired Team Plasma. It’s perfect for the region.
The problem with Unova is that it's not the U.S specifically, (Well, it IS New York, but not entirely). It borrows from a lot of locations around the U.S that you wouldn't find in New York city proper, such as the relic castle in the desert resort, which clearly evokes more of a desert ruin vibe you'd find near New Mexico or someplace closer to the equator. Humilau City is too warm an area for a place like Unova which should've stuck with the colder climate because it's Alola before Alola. In Legends Arceus they have the advantage of there already being ruins in the future Sinnoh, so it would make logical sense that they would appear more pristine in the past.
Some of the Swords of Justice do indeed mention the fire, but they also mention castles, which are oddly out of place in a setting like New York City,
to quote Terrakion's dex entry in B2W2
"Spoken of in legend, this Pokémon used its phenomenal power to destroy a castle in its effort to protect Pokémon."
And this was made in gen 5, Galar wouldn't come to fruition until much later so they couldn't have thought about that at the time. All I can say is I'm curious to see how they'll butcher the history of my homeland if they do make a legends Unova game.