I think I would remake Vagrant Story.
I havnt even finished it yet but the story so far is great and despite a few chores the gameplay is very deep and fun.
The most important change would probably be making weapon and shield switching a lot quicker and easier. I would probably implement a weapon switching system a la Metal Gear Solid where you hold down a button and it brings up the weapons while pausing the game. This would make the gameplay a LOT quicker because switching weapons for each enemy type was pretty tedious after a while.
But I would keep so that you still needed to specialise one weapon for each monster type.
I would make the graphics top notch but especially so that you can tell what type of monster it is and have a good guess at whether to use piercing, edged or blunt weapons against it. AKA, show whether it has chainmail on or a hard scale so you know you need to use a piercing weapon.

I would use FFXII's voice actors.

I would change the setting a bit so your not fighting in bland dungeons all the time.

I would make magic more useful than it is in the original. I would make it so that the RISK meter does not decrease your chance of successfully casting magic but instead up the MP cost.

Cant think of anything else at the moment.