If only I could manage to get Quistis to do her limit breaks, hers are by far the most powerful ones i have

You mentioned you have Aura, so you should be able to get limit breaks for any specific character! Cast Aura on Quistis, then, when her turn comes, cancel out of her action menu if you're not getting the limit break option; that should immediately reload the action menu and recalculate whether you can use a limit break. Just keep reloading the menu until the limit break pops up; if you have Aura status on, it should only take a few refreshes.

Good luck!