In the Alpha version of this game, the GCD timers were way too short, making it seem like a button mashing fest with abilities and was also unbalanced.
It was one of the biggest complaints during testing.
It would be game shattering since this would remove certain materia from the game and skill speed is no longer an attribute.
Not many casual players can press 30 buttons in .5 seconds for consistently high dps on a controller, so you will need a keyboard...but then you would need macros...