Well, there are limit break scripts (or OverDrive scripts) here in the forum. But they don't change the skill used by level, nor change the 'command' in the battlesystem's command window. What they do is disable the skill(s) tagged until the gradient bar is filled... then they get enabled.
Check the FORUM SCRIPT LISTINGS (in my sig) for a list of available scripts. You may wanna check the Custom Battle Add-On section -or- Skill Related sections for these scripts. It's not as big as it was prior to the recent downtime (duh... 400 down to 350), but it's getting better.
Trickster's Limit Break script is in the 'Unsorted Scripts' spoiler most likely as it was added after the current backup.