In reality I am much in the same mindset as Moose. I would like a more down to earth sort of story, where we go somewhere where we aren't known. We struggle again/get barred by leaders we haven't met. Maybe a trusty Alisaie or Alphinaud along for the journey. Meracydia interests me greatly. I'd also very much like an underground similar to the one in FFIV(which I don't think we'll really be getting, Labyrinthos be damned!).
But if we absolutely must raise the stakes again and go insane... let us forsake time travel. Let me revive Midgardsormr and ride his flaming mane unto the stars, back to the Dragonstar, back to bring the dragons their homeland restored. Let me fight and defeat what's left of Omega's civilization. Let me go be an alien to some race of people that we've only heard about through implication and data recordings. Maybe let me carry Alpha and Omega in my knapsack, such that they can both become major characters for an ark of the main story.
I'd rather leave the Source and its Shards behind completely if the story must become ever more outlandish. Let it truly, literally be outlandish.