I was just thinking about ways to change around the FFVII experience and game dynamic, and I was wondering how hard it would be to rework the materia system. So that instead of, say, two linked materia, you could have three, or binding elements and effect materia to armor/weapons would have more noticeable effects.
Personally, I think that there's a lot more potential for growth in the materia system than the game capitalized on--imagine a double-elemental attack, or materia that gives higher defense as the user gets weaker, or better weapon-doubling (no shields), or just holding two shields (that wasn't possible in VII, was it?) You could have materia effects that were dependant on what materia teammates were holding, or you could change the elemental holding of a summon. You could set a shield to perform an enemy skill when the shield blocks an attack, or who-knows-what -else...even make a character incapable of attacking, and only counterattacking when attacked.
I know this is probably complicated stuff, but I thought I'd throw the idea out there. It's started things before...