Personally I don't think it is that hard though I believe all our hands are tied.
There are two things which have to be considered for any new system. They are:
1) Controllability
2) Flexibility
As a pilot there is only one thing I can control when it comes to ATC flow management and that is what time we actually cross the feeder fix. Simply, the earlier I know, the more efficiently I can achieve that. If I have to hold inevitably so be it, though I shouldn't be told this approaching TOD. Personally I would like to be given an estimated crossing time on first contact with centre.
What I can't understand is why the system is not robust enough to allow for this? Ok, yes with 2 or 3 minute feed requirements and close in departures, weather diversions and go arounds the flow will change, however what I would like to see is a system developed that manages capacity. If too many aircraft are going to cross the feeder fix at time X and delays are developing greater than a couple of minutes, let the other guys know on departure well before the bottle neck, or before departure. We do it for Bad weather say between BNE and SYD with start approvals, why is it not the norm?
One method I find works quite well is the expected landing time.
"xxx123 Delays into Melbourne, expect landing time 0123, speed reductions approved"
Controllers, Just so you know when I hear this, this is what I do:
If it's a long week:
1. Select RTA Melbourne
2. Enter 0123
or
If it's not a long week
1. Assess the expected delay.
2. Reduce Cost index --> Assess time
3. Reaching CI 0, reduce descent speed to the minimum --> Assess Time
4. Reduce Airspeed from Max Range to Max endurance --> Assess time
5. Descend to a lower lever maintaining Max Endurance for an associated reduction in TAS/GS (dependant on forecast wind), to hold in a straight line.
6. Let ATC know if unable to make the crossing time.
Either way, the preference will always be to hold in a straight line at my most efficient holding altitude if need be with vectors/holding as a last resort.
I just wish the system had enough maturity and resources to have the information passed down the line earlier rather than later.