Kind of confused here, as I don't see the issue with nesting. Suppose, for example, work sends me on a three-week trip -- work pays for the home-away location-home ticket at the corporate discount rate, with outbound/inbound spaced three weeks apart. Two weeks into the three week trip, I decide to buy a leisure ticket to visit Mom or even go home for the weekend. I can't see how the airlines could have an issue or even quite frankly, any say, with that, as they're both legit tickets.