While I think about it, there is a little annoyance involving the Materia section. I think it has been mentionned earlier, but I thought I'd bring this up again.
Let's imagine you want to reduce the number of spells available in a certain materia. I'll take Destruct as an example. Currently, the materia has 3 spells : DeBarrier, Despell and Death. Let's try and reduce that to just Debarrier and Despell.
It involves deleting the '24' in 'Materia Type Modifier 3', and the level 4 Total AP amount ('450'). Problem is, you can delete 24, but 450 won't go away by just deleting the number. Sure you can do that, but as soon as you select another materia and go back to Destruct, you'll notice the 450 is back. Same thing if you save and reload the kernel. So, in our example, the only way (aside from using a hex editor, of course) to remove Death, is to put the amount of AP needed to learn the previous magic (in this example, Despell) in place of our 450. In game, the materia will still have the same number of levels, but the final two stars will be obtained at the same time.
Slight annoyance, but if an amount of AP could be blanked out, it would look better in-game and clear some player-confusion ("huh ? The materia has only two magics but it has four stars ?!").