Our next suggestion is the short Windsor and Eton Central Branch Line. The Slough–Windsor & Eton line is a branch railway line 2 miles 63 chains (4.5 km) long, in Berkshire, England. Trains run between the line's only two stations, Slough and Windsor & Eton Central. At its northern end, the branch line joins the Great Western Main Line, but passenger trains from Windsor rarely use the connection, usually terminating at Slough. The station at Windsor was once far more extensive than today and is the other part of this suggestion. Windsor branch map. Windsor branch bay at Slough. Windsor Central in its current form. The much larger Windsor Central during the downsizing showing multiple platforms.
With the greatest respect, no. That's a line I used to use a lot and it's a very boring short journey. Yes, it would be great to add it to the current GWE route as a free extension, but totally pointless building as a standalone mini route, sorry. At least if it was added to GWE, you could run the ECS service to/from Reading at the start and end of day.
Nobody would buy it because it won't happen. Two stations, lots of custom scenery, it would be financially unviable. Your best hope is if someone from the community did it for free.
Then bar what I suggested in the last post it isn't happening. If you want a GWR branchline, the only one that would make any sense is the Marlow Donkey. At least that would last a few minutes and have the fun of changing cabs at Bourne End.
I live in Windsor and I can assure you this shuttle service is anything but boring, at least in terms of sights. It starts at Windsor right near the castle (the most visited tourist attraction in England outside London), the views from the train include Alexandra gardens with its bandstand, a replica hawker hurricane (a memorial to Sir Sydney Camm its designer), the river Thames, Brunel's viaduct which I believe was once the longest in Britain, the playing fields of Eton, Eton College (in the distance), the Eton observatory, Eton Golf Course, the Jubilee river, and, if you are into this sort of thing, the M4 and Chalvey dump! I agree it will never get made, which is a pity especially as I would love to have seen the older and bigger central station modelled, but I have to take issue with the person who said it was boring. I agree there are probably more enjoyable branch lines to drive than this but I doubt if there are any with more interesting sights over such a short distance. Also if they ever make Windsor & Eton Riverside to Waterloo then you could route hop between the Windsor stations!