I agree with much of your analysis (ages back, I started this yesterday)
  Re partial agreement SDocs diet. In spite of the division that sometimes (often!) occurs on here.  I  actually don't know of  any  people  on here who  use a very low fat diet / high carb diet . This would  normally be  20% or fewer calories from fat.  Ornish's heart diet is only 11%  from fat with 71% from carbs. I've come across   T2 vegans/vegetarians elsewhere who have claimed to successfully use this sort of diet
The opposite is the very low carb and high fat (80%fat 18% protein and 2% carb) or the Bernstein 6, 12,12 diet.   Again, I've seen only a handful of people  who actually use this sort of diet on diabetes forums.
Most peoples diets  seem to be  somewhere in between the two.  There is  certainly no way could you eat Southport Docs vegetable soups on the lowest carb diets.  Indeed, Bernstein quite explicitly forbids it and even limits tomatoes  to a slice. On the other hand,  people who eat any animal products would find it very hard to adopt the very lowest fat, with consequent higher carbs and often very much higher fibre than most people are used to eating.(look up the Ma Pi 2 diabetes diet)
Given that most people aren't at the extremes , it's not surprising that many people see at least  some similarity between their own and Southport Docs fairly moderate diet. (and yes I do too!)
One place in your post  I'd comment on is this:
" "controversial" non standard "low carb" advice is to up natural saturated fats (eggs, cheese, butter etc).....
  agree  that is very  controversial
  However there are fats other than sat fats . I  think that most things I have read recently still suggest that Sat fats tend to raise LDL and  suggest replacing sat fats with  polyunsaturated fats  rather than carbs  (particularly any sort of refined carbs)
  The Mediterranean diet is relatively high in fat but that fat is mainly  monounsaturated . The successful  (re CVD)  Predimed  diet  contained  about 20% of cal from monounsaturated, 10% from sat fat and 7% from polyunsatfat . These were mainly  from olive oil, nuts, and fish,  the diets tended to emphasise white rather than red and processed meats plus fruit, veg, legumes, real whole grains and some dairy.  The Lyon heart trial  with a similar diet (though they  used rapeseed margarine rather than olive oil)  was also very successful.  (the BMJ article that was  headlined in  yesterdays newspaper articles  comments,  favourably on those trials 

)
However, as you say  there is a gap between the  38/40% fat contained in the  Med diet and one of 60+%.
That's where I would  think more carbs in the shape of  more veg, possibly more low GI fruits  but particularly more legumes (their properties were discussed elsewhere on the thread by Yorkman). The people on the Predimed diet ate 3+ portions of legumes a week.