From http://forum.square-enix.com/ffxiv/t...l=1#post155331

I want to be able to perform actions and cast spells immediately.
Although you'll still have to wait while in the middle of performing actions and casting spells, we're looking into allowing instant execution of actions and spells while in auto-attack mode.

Because of the restrictions of the stamina gauge, I can't execute actions with various special effects when I need to.
We are planning to remove the stamina gauge. Like before, TP and MP abilities will still be affected by recast times. There will also be cooldown times between actions.

After mistakenly choosing an action, or deciding to use a different action, there's no way to cancel a previously selected action.
This is somewhat related to the items brought up above in that once we change over to a gameplay style that allows for immediate execution of commands, this should no longer be an issue (since there won't even be an opportunity to cancel something to begin with).