Scott - as usual a thorough analysis, but I'm not clear whether this a response to post #1 or later ones?
To answer on my points - IF we were given the restrictions with the descent clearance our lives would be easier.
My 'contingency' figures were what I used against what the PLOG calculates as the airline 'minimum', and quoted only to show the significance of the early descents.
There is still a need for airlines (I refer to UK - I have no experience of the US) to have some way of predicting non-economic and fuel wasting UK descent profiles, and as I have said to those who kindly responded with information by PM, I now consider this to be of enough relevance to 'safety' as to warrant an approach to CHIRP in the hope they can communicate with SRG (ATC) to try and get some BASIC idea of descent gates into our planning system (Jeppesen in my case). EXACT altitudes are not needed, and can, indeed, change on a day-to-day basis if need-be, but we need some idea of where top of descent is going to be.
Edit to add I have raised a query through Chirp