Maybe Shin-Ra starts gathering the Huge Materia earlier this go. They've already introduced in VIIR that Scarlet wants something like it, and even the original game had her bring it up well before Meteor appeared
Yeah, I noticed this as well while replaying, Scarlet is already out looking for huge materia when you get to Gongaga, long before the weapons are even a thing. Having that is a parallel plotline could work as a way to extend playtime without it feeling like events are too far spaced.
The number of parts will depend largely on their release strategy. Nomura mentioned being a fan of releasing smaller games to get content out faster.
I personally would prefer the larger releases so I could get lost in the world of FF7 for a longer duration. If they go the longer route, my guess and hope would be four parts.
I concur with preferring longer releases. I actually like the idea that when the next episode comes the previous one will be long enough ago to almost make me feel nostalgic. I don't need to stay in the hype between releases, I enjoy getting to get excited again.
I'm curious if they went through the trouble to make it accurate for a few seconds of a shot. Especially if at the time they might not have been exactly sure how to do the world beyond Midgar.
I sincerely doubt it. In fact, I'd be willing to wager on it. They probably told the modeler to just make it kinda like the original map, but I don't believe for a second that they went out of their way to predefine what the world would look like, and stick to it, just for that one scene. They're not only not bound to the geography of that particular model, I doubt they even take it into consideration. I also doubt that the layout outside of Midgar will match the opening shot. It will probably look similar, but not the same topology.
Remember, we also see a model of the planet in Bugenhagens astronomy tower back in the day, and I am pretty sure that wasn't accurate either.