This is pretty much how I view it will be implemented/hope it is implemented.
DOL's go and farm Aetheryte Rich Crystals from fishing, botanist and Mining.
Each Crystal has a color cooresponding to a stat. Red Strength, Purple Dexterity, Yellow Vitality etc.
Disciples of hand take the crystals and cut them into Materia.
A Player with armor or weapons with a Materia Slot goes to a Crafter and buys the Materia and the crafter places the materia into his armor/weapon in a system similar to the Repair System. Attaching Materia also fully repairs the item. But the item becomes untradable/unsellable in the wards.
Materia Equipped gives a stat or a trait.
Red can give Strength, Attack Power, or new traits only available in Materia like Double Attack (A single ability acts as if it hits twice for a chance) etc.
Mixing the same color twice on an item makes the effect of both more powerful (red 1+ Str) + (Red 5+ Attack Power) = (2+Str and +7 Attack Power) Mixing opposing colors spreads out the effect adding a variable stat based on the mix. (Red 1+ Str) + (Yellow 5+ Defense Power) = (1+ Str , 5+ Defense, +Parry Chance)