I am not quite certain that I understand what the green chain is.
Looking at the final photograph, it appears to be a facility to sort and grade the lumber as it comes out of the mill.
That would be easy to add as an extension.
The one in the photo appears to be a roller table.
I was already planning, space permitting, a raised loading dock.
I find that I may have room for a single stall engine house that I more or less inherited from John.
He passed it to me with instructions to do some minor repairs, which I didn't get to before he passed away.
John stated that it had been built by John Labbe, which is pretty cool.
But there is nothing on the model to verify that and it is a bit difficult for me to ask either one for further details.
Sorry that the Labbe enginehouse/shops will not fit your mill scene.
Shame as it looked pretty authentic.
There are three smallish engine house plans I have in my collection :-
1. A Russ Simpson plan of the Graeagle Lumber single stall barn and shops.
This measures a prototype 60’ x 80’
2. In the “Logging Modelers Handbook” there is a two stall version as used by the McGoldrick Lumber Co.
This is 32’ x 74’
3. In Robert Turner’s “Logging by Rail” on p87 there's a plan of International Timber 2 stall loco and car shop with machine shop extension.
This measures 65’x80’. The loco single stall as part of this is 25’ wide
I can scan these for you if any is any good.
As far as kits I have always thought the old Muir Models Quincy engine house kit would be good if they are still available.
I think it was used by the Quincy Lumber Co in CA for a number of years.