I have an idea for a FF7 mod. One of the problems I see in the game is that characters become more or less interchangeable given how they can equip any materia. The only thing that sets them apart are the slight stat differences, limit breaks and weapons (slots, power, type). You can pretty much move all the materias between characters and have them fulfilling the same battle roles.
So, I don't know if this would be too hard, but have the materia levels be related to each character. Example: the Fire materia. Cloud had this materia equipped until it reached level 4, but then he removes it and some other character equips the same materia, but this character never used the Fire materia, so it is level 1 for him.
It is like, instead of evolving the materia, the character evolves his mastery of the materia. This would force each character to have a specific role in the game. Like healer, support, offensive magic, etc. It would be kinda like the job system, but more flexible.
I think some small things could be fixed, like the learning rate (could be increased), the time at which you get each materia (maybe getting some materias earlier, or coming with the character), the status change for each materia (change the values to significant bonuses), maintain the mastery for every materia of the same kind (if cloud reached level 4 with a fire materia, he should be level 4 for any fire materia).
The status changes I think could be interesting, because it could really change the character during the battles.
I can see this putting a whole new spin go the game. I have very, very basic notions of programming, but I would gladly helping in balancing and testing this mod.
Oh yeah, and one last thing, removing the damned damage cap, which is a total game breaker for later in the game. Some spells become a waster of MP because of the damage cap.