Wow. Not at all. Isshu is almost definitely larger than Sinnoh.
I think that'd be sweet. I honestly believe what the Pokemon games need is more Pokemon vs. Environment interaction. We've had things like the Snorlax blocking the road, Diglett destroying a man's property, Mewtwo totally obliterating the Lab at Cinnabar, and like you mentioned, Voltorb/Electrode acting as traps/power supply for various buildings, and so on. Things like that have diminished since then, with things like Sudowoodo and Keckleon blocking various passageways and Wailmer blocking the water route to Mossdeep... and not much else.
I'd like for more of that to happen in Isshu, with things more innovative than "X Pokemon blocking Y passageway". I originally hoped that a Zoroark sidequest would involve investigating a mischievous Zoroark that uses it's Illusion ability to cause trouble (which seems unlikely considering Zoroark's weird event now), and for Hihidaruma to be going wild in a particular location because it's habitat has been disturbed, and for a location in Isshu being a moving forest composed of migratory Torterra, and so on. The Pokemon world would seem a lot more cohesive if the Pokemon actually interacted with the environment rather than just being encountered monsters you see while walking through grass.
That wouldn't be an "achievement" if you were only able to catch these Pokemon with special Pokeballs that are given for the sole purpose of catching those unnecessarily-hard-to-get Pokemon. That's like saying obtaining a Riolu egg in DPPt is an "achievement."
I like the idea of a roaming Legendary that's activated upon getting your Starter. I think it'd be cool if that Legendary could be encountered throughout the storyline, but you were unable to catch it ("The Pokeball was deflected by a mysterious energy!" or "It's no use! The Pokeball isn't functioning!") until a specific in-game event that occurred late in the story or post-game... at which point the Roamer would become a Stationary. Think: Suicune in Crystal, only it doesn't just appear, you literally encounter it.
I think it'd also be cool if that Legendary fought alongside you to beat some sort of villain. Like, the Legendary comes to your aid later in the story while you're approached by a particularly nasty member of the Isshu crime group and double-teams the criminal (or perhaps joins in with two of your Pokemon to make it a three vs. three) with you.
I would adore something like that happening.
