I didn't say that FF characters can't use magic. If their magical abilities are natural, they can use them. For example, Vivi uses magic because it comes from within himself. Cloud, on the other hand, relies upon Materia for the use of magic. In that instance, one would simply assume that Cloud has access to every single magic spell in the game, on top of immense physical offense and defense capabilities. He can heal himself nearly constantly, and an destroy his opponent in a matter of minutes with Knights of The Round. So, where does it balance out? It doesn't.

As for FF10 characters, you know just as well as I do which abilities are designed specifically for certain characters, Carlos. Every character in that game starts out in a different location on the Skill Grid, and they have a section that is arbitrarily deemed "theirs." Those character-specific skills are fine. Crossing over into other characters' territory is not.

To summarize, if the character can naturally use magic, they can cast it here. If they gain the ability to summon or cast magic from Materia, Espers or Guardian Forces, then it's not allowed. Those are the breaks. I'm tired of hearing people post "This fight ends in three seconds. Cloud casts Ultima, Cloud wins." That's not fun, that's not balanced, that's not fair.