Mixed mode is needed now to help to alleviate the current arrival and departure delays, without deploying additional capacity. It is the wake vortex rules which are the current limiting factor, interleaving take offs and landings will be a major factor in reducing the continual waste of fuel involved in the stacking of arrivals throughout the day, a situation that the environmental lobby seems happy with as it is never mentioned by them.
In order to alleviate arrival noise, all the new technologies which are available should be deployed. A true 4D arrival planning should be instituted with EATs issued to aircraft to permit longitudinal holding if required. There is absolutely no need for arrivals to be directed to a 15 mile extended centre line over central London. There should be a fan of RNAV arrivals aiming at a final point at 5 miles with the spacing controlled by one of the available radar arrival sequencers. Indeed the opposite runway SIDs could be reversed to provide noise preferential arrivals, easy to achieve with current technology.
My impression is that these alleviations are not being opposed by the pilots or the operators but by those in charge of the ground environment who tend to resist anything which has a hint of deskilling.