I started a mercenary company in another online game that didn't support any such thing and if someone would need to hire one of our guys due to a lacking element in their unit, we just took game-cash payment. Later on after we started building a reputation with different companies they'd request our services more and more if someone couldn't make it and they started giving us loot if we needed it and included us in the draws for what we didn't need. It helped them because if we were geared better, their missions went better.
I think something like this could work well in for the most part in MWO because we'll have on average a higher class player base than many online games. I don't think it's just my personal opinion that there's higher caliber of people on the whole the more specialized the game is. And keeping it off console systems helps in that. I see more mature players in Battlefield than in Call of Duty and in Red Orchestra I've never seen people act disrespectful. But call of duty is made to appeal to a younger player base than Battlefield and people in Red Orchestra are there because of a love for the game despite any flaws it may have. They've sought that game specifically knowing what it's going to offer to them. Any Battletech game is going to have a similar thing going on with a dedicated people following it. Just look at the forums here. When someone trolls (which is less than I've ever seen on the internet) people don't feed their egos and they don't last long.
I've gotten off subject here, but I guess the point is that I think an honor system would work in our case. And if someone screws you over then spread the word to your mercenary/lone wolf buddies and don't give them business!