So let me make sure I have this system straight, it works like this correct? :

1. Use gear to increase "attachment points".
2. Once a gear has reached 100% you can convert it into materia.
3. Crafters can slot a single materia into any gear using the catalyst at 100% success rate. (they hinted in another post that there may be ways to add more with high failure rates).
4. If you want to take the materia out, you keep the gear and lose the materia.
5. Materia will keep Unique/Untradable status if the gear it comes from had it.