If there are any WoW veterans out there, you may understand this topic better than most.
World of Warcraft had an event called Cataclysm that ended up changing the gameworld. When players logged into the game after it, they found so many amazing changes. It was a phenomenal event and I for one, was gobsmacked. All the old familiar terrain was altered. One of the biggest was the grand canyon like zone called Thousand Needles became completely flooded and turned into an underwater biome. It made the entire playerbase feel like wide-eyed newbies as we explored the world to see the changes. There were new NPCs, new missions, a couple new races to play, it was a real content explosion.
The reason I'm mentioning this here is because Titan City will be one of the main characters in the game. I would like ot see it go thorugh something similar.
Remember how, according to the lore, Hurricane Atlas struck in 1998 and decimated much of the city. It was the result of a villain's work.
Now here we are thirty years later in the new Titam City. Our missions are sparsely sprinkled with clues from day one about some plot by one or various groups. It could include finding the remains of Atlas, or any number of McGuffins. The point is that during the first five years of City of Titans, we get missions every once in a while alluding to a new and serious villain or plot or whatever. Eventually the plot culminates in a huge anniversary event involving some enormous cataclysm like another Hurricane Atlas. Something that heroes can't stop, but we can save people from it, and stop villian groups tfrom taking advantage of people. Or maybe we work with villain groups in a pradigm-shifting we're all in this together sort of experience. (of course some villain characters can have their own special villainous missions during this event).
After this event, City of Titans reopens to a rebuilt and rebuilding city. The original map is full of redesigned neighborhoods, especially the beginning zones. This gives the developers an excuse to remodel zones in which they put their first effort and make the modifications and changes (in both the maps and the missions) that result from the lessons only five years of live online play by thousands of players can teach us.
It will also be a huge pull for all the players of CoT to come and check out the changes to the city they had come to know and love, just like how World of Warcraft brough back oodles of old players with their Cataclysm event.
To pull it off well, it has to have been set up from the beginning in the missions we all run as low level players all the way up to the end in one long 5 year spanning story arc, revealing itself as more and more city zones and updates are published.
I like to take your ideas and supersize them. This isn't criticism, it is flattery. I come with nothing but good will and a spirit of team-building. If you take what I write any other way, that is probably just because I wasn't very clear.