SE. I seriously hope these ideas, which I believe even a few of the ComReps have commented on in the past, don't fall through the cracks.
I would love to see a train system built into the game that players can ride betwixt all the cities and has a chance to turn into a Doom Train Encounter, with a time limit to rush towards the Engine Car and a fight to break out with the engine and the Skeleton mobs that are operating it.
I'd also like to eventually get to explore one of the moons like we've done in multiple past FF's. They were always interesting events in those games.