One thing you have to remember though, MMOs Stories in general assume the Player is One of a Kind. Each other player, assumed by story, are the equivalent of NPC adventurers to YOUR story.
This means that there is only one definitive character who enters the CIty State, that the Scions recruit them (effectively Before Ifrit) and that to help bluster the Grand
Companies you are asked to join one AS a Scion. Otherwise the Scions have the Army of Absolute Victory at their desposal because HOW MANY PCs ARE THERE? lol Because of this, you can go and say "I know I'm from Maelstrom, but I changed my mind; Sir, reporting to duty for the Flames." And Bam! Scion is allowed to switch, a City citizen would not be. This is very important to keep in mind.
Additionally, while you're assumed to be from outside of Eorzea it is mostly to explain why no one remembers you if you're legacy; adding into the information they give you regarding it. But, it also means you can make a story for yourself that brought you to the start of the game.
This character here is a Highlander. She comes from Al Mhigo; she was an infant when Al Mhigo fell. I have a whole story for her explaining her hardships she faced before she set out to start her story, AND WHY she does. I even tweeked cannon to have some fun, living with a Seeker Tribe outside the Sagoli Desert. Playing with their lore a bit, and using a couple of my other alts that I had tinkered with in creator as side characters. It made for a very interesting mindset for her, going out into the world when I look at storylines as an RPer.
