I can't really see the purpose, either. It basically sounds like you want higher leveled materia? Maybe in time. I think any dropped items in the game purposely do not have any materia slots because they are supposed to be "unique" items that aren't customizable. I'm sure later they'll introduce crafted items (never equal to the top tier, but increasing in level as raid gear increases) that you can customize with materia.

Also, AF2 isn't going to be released until 2.2 or 2.3. What is currently in game (Myth gear) is AF+1 (just like our Relics went from a +1 to a Zenith).