Ah, musta missed it.
Maybe this was already discussed too, but I'm still not sure I quite grasp the logistics of this.
How will the game inform the player what's happened?
You could tell people in a live letter, sure, but how will this new system be conveyed to players in game? It's not like you can have an AST main log in one day and see they suddenly have a level 80 Thaumaturge.
And how would that relationship work the other way?
If a BLM main logged in and had a level 80 AST, would it just come with the soul crystal?
Or would you need to have both jobs started and you could then take a quest to couple them?
Where would the quest be? In the AST guild, the BLM guild, or would there be a new place full of NPCs that just give coupling quests?
And I know this is kind of an off point question, and you've said
but wouldn't it be easier to just have new jobs couple to existing ones like SCH did with SMN?
Add Rune Fencer? Couple that to RDM.
Add Ranger? Couple to BRD.
Add Salve Maker (or whatever)? Couple to MCH.