Without meaning to derail this thread and open this well-known can of worms, yes it is possible, it just takes the will to do so. I don't know what you specifically mean by 'practical', though. Yes, LHR is higher, but there is no reason you cannot separately handle F class passengers and segregate them from the rest of the passengers. It would be expensive, but it is possible. There was a lot of internal opposition to the FRA plans as well, but it has proven to be an excellent service that is among the very best in the world.