I would respectfully submit an additional theory as to lack of such models.
And there are a great many other locos that at first thought one wnders why no one has manufactured them - Great Western #90, still in regular scheduled, nearly daily service, nearly all year long at Strasburg? Why is there not a model of that?
Respectfully, I would suggest that most manufacturers of HO models know that collectors are not their biggest market - modelers are.
True there has been a significant growth in "HO collecting" in the last decade or two, but I suspect that trend has already slowed with the economy just like several O guage dealers have reported to me about their sales of Lionel and MTH in that scale.
A collector with a big bank roll wll by the "famous" locos - Big Boys, GG1's, K4's, etc. - but usually only one of each.
A serious modeler with big bankroll will by fleets of locos to populate a working layout in a realistic manner.
There are a great many locos that I have more than 6 copies of - to give that big railroad feel to my roster and a sense of continuity to the layout.
Who is a more profitable customer for a manufacturer? Someone like me who buys:
9 - USRA 4-8-2's
8 - Baldwin 2-8-0's
4 - USRA 2-6-6-2's
2 - USRA 2-8-8-2's
6 - EMD GP7's
8 - ALCO FA1's
6 - ALCO FA2's
14 - EMD F7's
3 - EMD FP7's
OR the guy who buys the same total number of locos but every one is different?
The manufacturer made way more money on me because they sold more locos with way less tooling cost. Extrapolate that out over tens of thousands of customers - which customers do you really want - the guy who buys one or the guy who buys 9 of each item you release?
Sure, in recent history manufacturers have worked hard to hit BOTH markets at the same time with each new offering.
But a product that is seen as only having collector interest and only having a small modeling following would be a very big risk - even for brass manufacturer.
Some guys "model" and "collect", and if they have money the manufactuers love them.
But many like myself only/mostly buy what fits the theme of the layout - I would not buy any of the locos you mentioned - not even at Bachmann prices let alone brass.
I do not own one - Big Boy, NYC Hudson, GG1, PRR K4, UP Challenger, UP FEF, PRR Centipeed, Triplex, N&W Class J, CPR anything, etc, etc.
I don't buy models just because they are "famous" or still in operation, and niether do most of the modelers I know.
I don't think that market is really as big as you think.