As a comparative newcommer to the garden railway scene, I find this historical thread quite interesting from a human behavioral point of view.
This whole subject of the developement and choices of model railway scales and gauges through the ages, seems to me to be a wonderful example of Darwins theory of Evolution and Natural Selection as it passes through cicumstances that are largely independant of the distortions of commercial, economic or social cconsiderations.
What we are seeing here is a natural progression of the reasons for, and consequences of, a variety of historical choices that could only have been made based on the technical knowledge available at the time, with little consideration given to the myriad different ways that the future of our hobby could develop.
The consequence of this is that we are now precicely where we could expect to be in an ever changing and evolving world, especialy if you believe - as the line in the famous poem goes - "no doubt the universe is unfolding as it should"
So it seems to me that the relatively little change that has occured over the timescale of this thread could indicate that well intentioned folk are spending far too much time attempting to speed up this rate of change with very little to show for their efforts.
I'm afraid that when people like David say ...... "My Pitch to Newcomers to G1 is that ScaleOne32 is well worth considering, it actually works better than the Vanilla stuff" ..... he is in danger of directing them down a path that may be totally unsuitable for newcomers and, at worst, could even lead them into an evolutionary culdesac - not to mention precluding the possibilitiy of venturing into the wonderful world of 16mm.
From a technical point of view, I'm quite surpised how well everything from the different manufactures and all the various sub-divisions within the hobby are working together. I can take a variety of gauge1 and 16mm models to numerous club and private tracks and rarely run into any of the kind of problems raised in this thread, apart from the occasional inconsistency in a nominal 10ft. radius curve - or too tight a radius on a set of points when trying to run something like a Pacific or larger, but all that means is that I might not be able to get it into a passing loop, no big deal. Or my narrow gauge wheels rattle on the G1 chairs, but that's only happened once in three years. Derailments can be a problem, but they seem to be more associated with a poor standard of track laying rather than the design configuration of points - or the matching of longitudinal overhangs of adjacent items of rolling stock is not as good as it should be.
One welcome develpment I see is that some clubs are now incorporating separate tracks for gauge 1 and 16mm trains into their facilities which can only make a good situation even better.