I see Innundo understands the role this alliance would play in society. I'm not sure mercenary works, but close. Imagine a group who joins one side of a battle or another, not for payment or even to support the cause, but simply that at that moment it suits our purposes, our fancy, our whim.
As for another alliance in No Man's Land... it would not bother me. I'm looking for a particular group of people. The location is representative of the people who would join, but they still have to be of a certain ilk.