A lot of what you ask for is already going on. Certainly at LHR we will be looking at the rest of the day and the next day for route bias and working with airlines to swap, say Frankfurt and Cologne flights from going out through Dover to Clacton (and vice versa), or on a southabout transatlantic day, requesting the Dublin flights go north rather than out through Compton.
The problem is that everything in terms of capacity planning has to be based on the planned 4D trajectory, and if that route isn’t followed (regardless of the fact it was given a short cut for the best of intentions), all that planning goes out the window.
We are moving from ‘first come, first served’ to ‘best planned, best served’.
If you you wait until an overload situation is developing to do something, it’s far too late.