So, let's speculate about future Story developments (SPOILERS!!!)

[Nalien]

What you're suggesting is that world-altering disasters can't be allowed to alter the world.

What world altering disasters? Even the Calamity was only really an Eorzean thing. There really aren't any world shattering events outside Garlemalds expansion in this game. The fate of Nanamo certainly isn't world altering...

The end of 2.x is an Ishgardian-altering disaster, hence we get to visit the place after several long years of waiting. How is that maintaining the status-quo? I just look at Revanants Toll and I'm fairly happy with how the world evolves over time as it is. Characters can come and go following disasters, the only issue is making quests they appear in requirements. Can I see them making the Culinarian quest a requirement from the upcoming Main Scenario so they can kill Nanamo off in a sensible way? Not at all. Can I see them making Crystal Tower a requirement somewhere down the line to bring back Nero (Who, I should point out, broke his status-quo as Cids mindless rival) and perhaps G'raha Tia? Absolutely. Likewise, the Main Scenario cast, apart from a few exceptions (like Nanamo) could potentially be killed off. So far the only mistake SE has made in that regard (SPOILERS) is introducing and killing off a character practically in the same paragraph. Someone like Yda who, to my knowledge hasn't appeared in any side quests, could easily be killed off in part 2 without it creating any plot holes and with it having significant impact because she's actually been there since day 1.

I do find the idea that the only way to create impact and break up the status-quo is to kill off characters to be fairly silly though. Like I said, having someone go through a character arc is much better storytelling. The status-quo for part two would be Nanamo surviving and being exactly the same. It would be much better to have her survive and actually become a significant leader with an actual personality. That would break the status-quo without defaulting to a lazy attempt at building emotion with a death and without creating a needless plot hole.

All I'm suggesting is that they don't need to, nor should they, create a stupid plot hole. They can change the status-quo without doing so.