In the case quoted above,
MXP-LGW
LGW-MXP
MXP-BCN
BCN-MXP
If all else is equal, weather, etc. I would split the sectors to 1 and 4 and 2 and 3, this gives a variety of different departures and arrivals then, like Piltdown Man, I would ask the FO what he wanted to do.