Yeah, no... there's a reason only classes have the ability to cross-class any cross-class ability and Jobs can't. The classes are meant to be the jacks-of-all-trades, Jobs specialists to a particular role. By giving Jobs the ability of classes, even if only for one ability, would damage the balance of said Jobs. Warriors with Invigorate would become incredibly potent tanks, much more so than they already are. And anything from rogue would be broken on any other Job.
