The Annihilator gives out a small amount of particles while charging, then releases a deadly and accurate blast as it's main attack.

For the digger, I think as it charges it should function as the Annihilator does, but with more particles so that it actually works as a digger.
Then, for it's unleash attack, it fires a short range but more powerful shockwave of better digger particles (Think the range/spread of the heavy digger). The wave would be for clearing materials that the charge particles could not destroy, like the metal in bunker modules.

Cool idea, I will work on it

edit: Look for the Trappers mod in mod releases