Hi, did you think about something similiar to Opening of Anh’Qiraj in WoW in your Living Story?
If you dont know what i mean, it was kind of realmwise quest, where all ppl on realm needed to do something to achieve next step in story, e.g. gather a lot of something, craft a lot of something etc and bring it to NPCs for a small bonus (something like LA repairs)… when realm collected everything what was needed, story evolved and new dungeon was open on that realm