don't think so, since this 'fights' will be like the existing ones between, let's say Hive and Fallen. The difference will be that the NPC Guardians will return to his respective place when the fight ends or the killed ones will vanish. [EDIT]: In fact, this can be addressed as public events. An with great variety, the defend outpost, the no Guardian must die, the open a breach for incoming Guardians, etc.