I think the materia crafting thing should be another craft job. In order for it to be affective though, it is paired with the other craft jobs already in the game.

Meaning you can't do it solo but could be paired with doing it with, lets say....leatherworker. On the recipes you can make on leatherworker, you can combine it with your rank on materia to enchant armor, tool, etc. based on what stat the player wants on it. And the higher rank you are in materia, the more stats/abilities you can enchant to that said armor, tool, etc.

I hope I did atleast a decent job in explaining what I mean.