Interesting map Will, explains a good deal, but also creates a couple of questions in my mind.
As I've said previously having been in the airspace for 8-9hrs, the system is aware via satcom datalink (which is used for and to determine separation outside of radar range...my understanding) of all the ETA's to the nearest minute.
If as you say the sequence isn't finalised until 250nm, then at what range is the planning started? Surely from a planning perspective, if something is finalised, then the starting point begins with the available information..i.e. aircraft already airborne and providing accurate estimates.
All things being equal, from a planning perspective, I would have thought that already inbound aircraft would be allocated their place in the sequence..and popup aircraft closer to destination estimating the feeder fix at an earlier time would merely be allocated an earlier time or advised of a delay. Given that the delay is now a known minimum quantity, why can't this be passed on? Yes we all know the environment is dynamic, yes by now I am aware that in terms of a plan..nothing is in place until I am practically on top of the airport....but a little bit of info helps.
The alternative based upon the explainations on here relating to finalising the plan is to merely fly at warpspeed and get to the front of the line before anyone else.
FWIW the other morning into MEL I was advised of our inbound delay about 40 minutes from destination, superb is a word I would describe the level of service I received on that particular day.