LOVE Sakura and the Aht Urhgan automatons. I'd love to see more trust magic along the lines of Sakura honestly, a few "minion" style alter egos you can call forth to add some useful passive buffs would be a lot of fun for me. I'm sure other players enjoy the benefits of melee and healer trust magic especially when levelling, but personally I tend to use trust magic when either farming crafting materials, or getting a handful of merit points solo and tend to use Sakura and the bards more than the other NPCs simply because they're relatively low-maintenance and I see more of a benefit from getting more buffs for my character than trying to let the alter egos do more of the work
I'm thrilled to hear we'll be getting a moogle and goblin alter-ego. While storyline NPCs are nice, I'd vote for more unusual types of alter egos (like cardians, Qiqirn, Meebles, Spriggans... craubables!?)