They'd be significantly weaker than limit breaks(considering DD lb's have retarded high potency) but still stronger than a normal attack so that its actually worth using. Can set the cooldown on it to like 5 minutes + or something so it cant be continuously abused. And these abilities could range wildly depending on the jobs/classes present since every job has unique abilities. Also they'd only be able to work if the skill is native to your job. Like for instance restrict them so that Even thoguh I can equip say Invigorate on MNK, my INvigorate would not be able to open a combo window for a band ability involving Invigorate. Only LNC/DRG's invigorate would open the combo window(im trying so hard not to say skill chain.)