Hi All,
In my world, on the Missouri Western Ry and the Colorado & Kansas Ry, my Bachmann Locomotives although narrow gauge as manufactured represent "standard gauge". In my world my Bachmann steamers run along side my standard gauge diesels. I use 1/29, 1/32, and sometimes 1/24th figures as long as they fit the scene. Any building that fits the scene works as well. Some say I'm crazy and to them I remind them, I am Loco and having fun with my trains.
If I wanted a WM three truck shay, I would just reletter a Bachmann Three truck Shay, maybe add or relocate a part or two like the prototype and call it OK. The one thing I have learned about our large scale hobby is that we will never have everything we want. My list of what I want is pretty long, too long to list here. My solution is to look at my layout and see if something on my want list really fits with what I am doing. If I see something on my list that I consider very important, I evaluate what I can do about it. Awhile back I wanted a short caboose, but with four wheel trucks for my logging line. After some thought, I realized that I could take the Bachmann eight wheel 4 window caboose and cut it down to a shorty four wheel truck one window caboose.

I fixed the hand rails and on some I made them with with steel wire. It turned out great and I made more, I still get great compliments on them. I learned that it was fun to make things no one else had.
My son runs the large scale California Zephyr using the USA TRains passenger cars. It bothered him for two years that there were no vista dome observation cars available. Finally he bought the dome section parts from USA trains and added it to his California Zephyr. He had never done a kitbash before, you could not tell the dome was added. Ican tell you everyone wants to know who made it! After that He took and alco PB and made the Steam Generator version of it as used on the Rio Grande Zephyr.
It never hurts to ask Bachmann to produce something, after all we might get a surprise one of these days.
In the meantime maybe give a try to getting that item you really want by kit bashing!
Enough musings for now!
Crazy Loco Bill

Have fun with your trains and stay cool!