Ok so I would want a lot of changes made. Rather it be new materia, characters, etc. First off I would want new graphics for everything but keep the main menu the same. If anything just update pics and themes. This would promise the remake is still going to have a decent system. I wouldn't mind them adding a few things to it. Somethings like 2 accessories or more materia slots is excusable.
As far as items go, I would want a lot more. I would like to see mega potions. Mega Ethers. Phoenix Pinions, HP Up, MP Up. Better growth weapons. Right now the best is apocalypse with three slots and triple AP. If everybody got a triple growth weapon on par with three slots or a 5 slot with double AP I'd be more then satisfied.
Armor could use some improving. Make all the stats work. Maybe add an area where you can get mystiles or other top tier stuff. So have some new locations where you can explore better. If they improve the game with extra content (which they should), I would suggest more materia. I got a forum here on that topic, http://home.eyesonff.com/showthread....ur-own-materia!
So I would want better weapons, better armor (or ways to get the best armors), more materia, and perhaps a better battle system. Where the character don't just step in front but more move around like in FFXIII.