I think is safe to assume since we are still in beta, that the dragoon using clouds limitbreak (Btw it was not omnislash) is a place holder, but we cannot be 100% sure since Kain in IV could use swords, maybe it has something to do with the weapon you are equipped currently which i would be very impress by, since not only could you have one job have different Limit Breaks, but potentially different effects etc etc.
What i would love to have dragoons limit break be, is as soon as you enter limit break, your dragoon jumps and as he comes down you see an aura of a dragon around your dragoon as he dives down to strike, and as he is close to hit, the dragon breath's an element aligned to your weapon, and your dragoon then delivers the jump hit, culminating in an explosion or some flashy thing.