At some point you guys have to just quit 3 rail and go to HO brass. Thats the only way you will get the details you desire.
If you look hard enough, even the best o scale engines are not like the real engines. There are way too many details on the real engines that just cant be replicated in any economy on a model selling 50 copies.
This is a fantasy scheme engine, to offer a painted model for NP fans, which there are very few of.
A train company just cant make a buisness case for specialized tooling for a few copies of an obscure engine that only two or three guys would order...