Velheart, you bring up great points but you descend into hyperbole. There is no way Square Enix would open up the cross class abilities without some adjustments.

Furthermore, this game is not a game where highest dps trumps all. Each encounter is a puzzle and the abilities we have are the tools we use to solve that puzzle. I feel my idea would free the developers to become even more creative in their encounter designs, particularly in light party content, because they wouldn't have to worry about the lack of a particular class and their abilities in an encounter.

Perhaps, it's as you say. That certain skills will be deemed mandatory and there will still be cookie cutter builds. But, I have learned one thing while playing games. Never underestimate the cleverness of a player when it comes to designing a character.