I'm sure this has been said already, but I would LOOOOOVE for them to add the first theme from Akh Afah Amphitheatre. I know everyone wants the second one, but I absolutely LOVE the variation that plays throughout the first phase. More than the second one, actually. >.>
https://www.youtube.com/watch?v=KhDldATuFQ4

Also, I don't know if this one has been added/suggested yet (I admittedly haven't done much in the way of digging around for Orchestrion stuff just yet ;;;; ), but I would like to see the Limsa Lominsa daytime music added. It's my favorite BGM in the game. ;;;;
https://www.youtube.com/watch?v=U7ForHMX-xs