Another fantastic idea! Thank you for mentioning it Metal! The Shunting Yard Shed is another structure that I would immediately put on my wishlist. It is in indeed a generic shed, but one that both young and old Thomas fans will remember. As has Metal mentioned, it has been present in both the Shunting Yard and Ffarquhar/Anopha Quarry, and would look fantastic next to the single engine shed that was announced in 2015.
https://vignette.wikia.nocookie.net/ttte/images/7/7b/Salty%27sSecret65.png/revision/latest?cb=20160817174313
I also see this one being possible because even though it is a double engine shed, it is shorter in length than the single engine shed.
http://ttte.wikia.com/wiki/Salty%27s_Secret/Gallery?file=Salty%27sSecret86.png
https://vignette.wikia.nocookie.net/ttte/images/7/7b/Salty%27sSecret65.png/revision/latest?cb=20160817174313
I also see this one being possible because even though it is a double engine shed, it is shorter in length than the single engine shed.
http://ttte.wikia.com/wiki/Salty%27s_Secret/Gallery?file=Salty%27sSecret86.png