So I may seem like a total idiot but I would like to see that the Guardians would be able to work for other factions for payment, (Fallen, Hive) but I can see how this won't make sense with the story as these two factions are part of the "Darkness". But of there were any other two factions in the full game why not? It would make sense if you were more powerful than one faction, they would attempt to try and get you on their side to help with their efforts to beat their enemies. PS: Sorry for grammar mistakes.