Enchanter:

Make a class that can craft small enchantment stones that would go alongside materia. Only one per piece. But the said enchantment could MAX out the entire possible stat for that piece.

Say I have a healer and want more critical chance. I could craft one of these "crit" enchantments, and place it on the armour piece. My crit would be maxed out, but I'd still have a way to keep the 5 materia for other stats. Or Maybe I want a "vitality" enchantment to make up for the lower vitality of the crafted gear over the raid gear.

For a level 10 enchantment you could only gain +10 of said stat, but for 60 you could gain 60 or whatnot. Then to make it "difficult" make it so that the mats for the high level enchantments only drop from the high end raids. Simply so that the best ones aren't easily accessible. I.E.

~Spell Speed
~Parry
~Vitality
~Critical rate

etc. And maybe exclude main stats, with the exception of the vitality.