I have read all of these posts with interest, but I think that I too must be a bit of a 'non-conformist', or at least rather eccentric!
One of my earliest memories is of walking and being pushed in my pushchair by my mother in a South London park, along the side of which was the soon to be closed Crystal Palace (High Level) branch - this dates my memory to around 1954 and no later. I can distinctly remember the smell of the Southern electrics and the sound of their brake pumps running. I was also held up on footbridges to look at passing steam trains - pretty much all freight since most that part of the Southern had been electrified for many years. Later I traveled daily to secondary school by train - also Southern EMU's.
So perhaps I might be expected to be modelling as Southern Electric layout - and although this is one aspect of my layout, it is set between 1938 and 1948 - certainly before I was born - and is predominantly Southern steam.
For many years I had no space or time for a layout but I started to steadily collect Southern loco's - mainly kit built because at this time there were almost none available RTR - such that by the time a significant, permanent layout became a possibility, I had so many locos that I decided that the goal would be have at least one of every loco type that the SR had in stock at nationalisation.
For this reason too, I decided that a single prototype was not appropriate, but rather, the location must immediately look and feel Southern - even when no rolling stock was to be seen, and so this is where I am now headed.
Whether I can achieve either objective - one of every loco type, and an immediate Southern feel, remains to be proven!
Best wishes
Tony