I think another issue has been that many international frequent flyers fly to more than one location. So an all-business airline would seem to work only when (1) it is materially less expensive and (2) there are enough regular flyers on that route to fill a plane. Otherwise, you might give your business to the few airlines that fly a lot of places, so the FF miles you accrue you can use for upgrades on those flights when available. I flew Openskies a few times years ago (when they were still all-business/first) from IAD, though I did not find it that much cheaper than AF or UA much of the time. I have not had an opportunity to fly Le Compagnie EWR to CDG, though their prices are, at least for now, significantly lower. I'd be interested to try it, but that is not a route I take often. But NY are probably has a lot of people who do.