'All of these models are subject to rangefinder flare.'
Whether or not that's a real problem is one of those things that varies from individual to individual. Some people manage to shift their eye so that the flare goes away - I've never come across an occurrence of it that couldn't be eliminated by moving the camera relative to my eye, but it does distract you for a split-second. The early M7s did not have the current M7 viewfinder when they came out of the factory.
Leica, and independent Leica repair people, can install the new viewfinders in old cameras. All sorts of magical transformations are possible. Leica USA charge USD 262.50 for the viewfinder replacement, others charge less.
Tom, I'm at a loss to know why a camera made in Germany has more appeal than a camera made in Canada. How about the ones, like your M6TTL, that were made in Portugal? Does the country of manufacture affect the quality of the photographs? Of course it doesn't (and I know that you aren't suggesting that it does). Please, can we leave that country-of-origin stuff for the camera collectors?
BTW of all the Ms I've ever used, the M7 is my personal favourite - and I've been using Ms, and their kid sisters, since '73. I have three at the moment - two to carry and one spare.