Kahza-Nirovsk is neutral. This can mean 2 things: either they are neutral because they provide humanitarian aid and refugee shelters (like the UN), or they play both sides of the war (aka mercenaries).
I'm inclined to think it's the latter... (see Seel Kaiser: Violent Victory poster)
So I'm thinking... Lennox and a Kahza (not necessarily Arden cause his char sheet didn't say so) founded the faction to earn big bucks, then when he and Manov got KIA, Sofer got pissed off at the group's inability to save them and stormed off to Tourbillon...
btw, i also see that Cort, Katrin and Niss had the armband but were not labeled as Pillar members... Maybe the armband is another yet-to-be-disclosed mystery?