Johto has a longer history than Sinnoh. Even if we went back ten centuries, they would still have loads to work with. This means they can't half-arse a Legends: Johto game like they admittedly did with Sinnoh's. We could back to 12th century Japan, during the Heian period, and we'd still have bustling settlements like Ecruteak City, Goldenrod City and Blackthorn City, all of which are very diverse culturally and geographically, well-established infrastructure, and an even richer history including the towers, Himeji Castle (Battle Frontier), Lake Biwa (Lake of Rage) and the Whirl Islands. If they decide to split it into seperate areas like Hisui, you could have woodlands (New Bark Town to Violet City), wetlands (Ruins of Alph to Goldenrod City), central hub (Ecruteak City), coast (Route 38 to Safari Zone Gate), mountains (Route 42 to Mt. Silver). It's true that Johto is not as geographically diverse as Sinnoh, but the landmarks they will be forced to work with, as opposed to simply being ignored as in Legends: Arceus, will for sure make up for it. They could also have sub-areas too, such as an autumn forest, at the foot of the mountain range area, a moorland with hills and farms in the coast area, even going as far as to extending into Hyogo, which wasn't present in the Johto games, a nature reserve area, acting as a primitive National Park, near Goldenrod City. Johto has a lot to work with, I don't know why people keep saying the oppisite.
