Yep i rad about rare/ex will nit be able to convert to mateia neither attach mTeriaon it. But... I read on japan forum translats the will be. Rare/ex equip will transform on rare/ex materia and they will be able to be attached whit materia. But the yoshi-p intention appareantly is to let normal weapons whit full materia be better than tiers2/3 whit full materia.

About the devce attaching 5 materias at once bt one-by-one and if u fail one step you die!!! Sounds... Good?

Btw i read too about loosing mateia, catalist and equipment too if fail. Agan on japan forums

I encorage you to see the second link of OP: reinheart translations of devs and yoshi rsponses.