Metro man, I think we are singing from the same hymn sheet but in different keys. I may not be a pilot but designing conferences for ATC, as well as other airline related topics, brought me into detailed contact with all levels from controllers to Directors General of ATC, from airline route planners, through pilots to airline CEOs.
I got the impression from the airlines that, given all the factors we have discussed, minimum time tracks were the most cost effective method of flying between long haul points using current technologies.
With regard to the North Atlantic tracks, I have spent time at Shanwick's Ballygirreen facility and worked closely with its Prestwick arm on conference topic planning concerning FANS.
The track system was designed as you state but the development of TCAS, dependable INS and ETOPs has, over the years, led to the introduction of RVSM, (which is now universal at altitude) and the number of random track clearances on the Atlantic has significantly increased. The current track system is almost totally weather driven to give the fastest crossing times.
Regarding Free Flight, I used to own and organise an ATC conference held in London. This was open to directors and senior managers of ATC, ATC equipment manufacturers and airline directors and was sponsored by major manufacturers and endorsed by the UK CAA and the FAA . In December 1995 at the Edwardian Hotel, Heathrow, L Lane Speck of the FAA announced to what can only be described as a disbelieving audience the results of David Hinson's FAA task force's report into Free Flight in US airspace and the planned implementation of the system, starting between FL360 and FL450 with a target of all airspace down to FL010 by 2002 and then down to 5000 feet outside terminal areas.
I was asked to design and organise a series of seminars to be held around the US and in March 1997 went to Washington to present my proposal. Prior to 9/11 I had jump seat privileges with a number of airlines and discussed Free Flight with a number of crews between 1996 and 1999. Few, had heard anything about it, the proposed timetable or the implementation of Stage One.
The seminars never took place and the implementation of Stage One was limited. Many reasons have been cited ranging from budget cuts by the Clinton administration through to opposition from the general aviation lobby which had concerns regarding the cost of mandatory equipment and the implementation of what they saw as an increase in regulation.
Since I retired, Free Flight has become Next Gen ATC in the US and is slowly being implemented. Dallas went live in November 2014 for instance. In Europe Gate to Gate 4D Trajectory Management is under intensive development. Both systems work on the basis of minimum time in the air.
Airlines see the benefits of shorter journey times, greater punctuality and savings in fuel and maintenance. Great circle routes may well have more usage under the new systems but the systems have been simulated on the basis of minimum time tracks taking into account weather, terrain and other variables.