I'm so anxiously awaiting this game that I had to register just to chime in.

Story was incredibly central to this game, so more more more!
-Explain what the deal was with Seigfried and Ziegfried.
-Side quest of finding out what happened to the Returners after the World is thrown in Ruin
-More hints as to the identity of Gogo.
-Make Shadows dreams worth something. I'd like to see a more definite ending. I know the original idea was he dies at the end. But the text made it seem like he wanted to live (in order not to depress kids). I'd like to see a "suicidal shadow" ending in it's entirety. BUT! If you gather all the dreams they could keep the original text and see Clyde walking through the countryside after the end credits.
-More on how Kefka got so deranged. It's supposed to start with him being the first experiment case for magic-infusing.

I'd like to see them touch up the text ala FFIV. Keep the classic lines "Son of a submariner!" while giving the spells back their proper names.

Music player of course.

I loved the extra dungeon from FFIV with the new weapons and baddies. Toss in some of that and see if it can't be worked into an Epilogue story. Maybe cross over villains from other FF's.

Don't make the game easier. The other FFGBA's have seemed too easy and disappointed. If you want to make the game tougher, eliminate the "Vanish/X-Zone" combo. Too easy.