P-J,
Hope you don't mind, but attached is a screen shot, containing what I would do in the first instance, and what could be done if there had to be a loop. An alternative with the upper plan would be to indicate a loop off at stage left, by having a little bit of the return curve before the turnout in the loop.
Basic idea is that the two sidings are used as the 3,3 part of the inglenook, and the loop run off (via the loop) for the 5 component. There is a short platform for handling general supplies and also a works passenger service if required.
Scenic treatment is fairly obvious, but I would resist the urge to fill the place with track.
I have used 1:7 turnouts and a minimum radius of about 87". Longer turnouts look better, a 1:7 is still quite sharp by prototype standards, and although you are currently thinking of small 0-4-0 tanks, you may get an itch for something a bit bigger in the future, and this would cope with that...
The Templot files were put together quickly, so niceties like timber shoving have not been performed, but for anyone wanting to play, I can email the box file.
Simon