Absolutely superb. I could have written that post word for word - you've hit the nail firmly on the head.
That's a great job with that Worsley coach above - what was the donor? If I can EVER get the time, I'd like to be doing something like that too.
Very interested to see how this will progress.
As for resemblance, those LNWR types had different panelling to anything here, especially the very distinctive styles of Inchicore and Broadstone, but some of them have roof and sode profiles, and window spacings, which look sufficiently MGWR-esque to pass muster under the 2ft rule; the above included. While MGWR bogies were gone by the late 60s, with all surviving wooden stock by then being ex-GSWR, there were significant numbers of them still in use in the 1950s, and many even made it into black'n'tan. I've seen a picture somewhere, probably in the IRRS, of a spotlessly newly-painted black'n'tan MGWR bogie side corridor main line coach. Black and tan on a Midland coach looks plain odd, and it didn't suit their panelling style at all, but there it was.
I see you're using the post-1955 green - that will make the lining a whole lot simpler, and if you're short of "flying snails", no worries - while the earlier dark green had snails on everything without fail, in the later livery some stock had snails and some didn't! Bit like steam loco tenders........