Until such stuff is available, cannibalise available kits. Actually, I doubt that purpose-made materials would cost any less in the long run.
As for concrete: Even in real life, the texture of the forms is hardly visible. Weathering tends to bring it out, as most forms are made with horizontal boards, and dirt etc will accumulate on the minute ledges that result. But forms are made to minimise such textures as much as possible. In fact, when the concrete is supposed to be heavily textured for aesthetic reasons, the forms are made with special materials that emphasise the texture. Weathering such as rust stains from bridge girders resting on piers tends to overwhelm the textures of the forms. Applying such weathering, and then dry brushing, will do a nice job of suggesting the texture you want. More than molded texture would, I think.
Anyhow, anyone contemplating satisfying your wishes would need to know the about how many purchasers of these products there would be, about how much the average purchase would be, and over what typical time span. Do you have any reasonably reliable estimates?
From what I can tell, most live steamers build one or two locomotives in a lifetime. That's a very small market. Maybe Gauge 1 build more? Maybe the live steam people could/should investigate farming out the production of parts to each other, and trade amongst themselves. That would guarantee that the production would be exactly what people want. Eg, you say you have built most of what you want anyhow -- couldn't you get in touch with other live steamers and offer to build, say, a pressure gauge in exchange for a couple wheel castings?
And I bet there are two or three "I wish I could builds" and two or three "I'll build one someday" for every live steamer who actually builds. ;-) I don't think the availability of more parts would change this very much.
Not surprising, when you consider the economics of producing for a small market. The local market is small overall, each producer has to have customers outside his local market.
Good for you!
"Where there's a will, there's a way." To quote Some Ancient Wise Person. ;-)
Siding similar to some of the Evergreen sheets only "roughened."
Rusty tin roofing material.
"Bulk packs" of windows, doors & other building details. I hate buying them four at a time & lots of places don't stock 6-8 packages of the same style. If you are building a building with lots of windows, you are usually in trouble.
Problem is that with most of this kind of stuff, what I want, you don't. That makes it pretty expensive to produce if there is only a limited demand. Personally, I like buildings with turrets & bay windows. So, I'd like to see a much wider selection of those kinds of detail parts. But if I'm only one of a few, then it makes no sense to make them.
I checked the Walthers HO scale catolg pp. 470-490; I didn't see that in their line-up, although it was all kits which were listed. Is that product beyond what's listed at Walthers? I see they have a catalog of products available.
The one things I have found for riveted plates is Golden Spike Industries (formerly Three Brothers) HO scale rivet sheet
Aster sells spare parts, but doesn't list them in the catalogs I've seen. They don't seem to sell parts for scratchbuilding specifically.
The question was what would I like to see, not what would I expect to see in a reasonable lifetime.
Maybe if more parts were available people would build more locomotives. Making all your own parts does take a significant amount of time.
That's exactly what has been done for quite some time. People exchange work for parts, and parts for work. Sometimes 2 or 3 people will get together to build models of the same loco, and split up the work according to who's best equipped to do certain things.
Probably not, but it might get the "I'd do it if I could find some parts" to do it.
I was mostly poking a little fun at people. Since I enjoy scratch building, even if more parts were available, I not sure I'd buy them.
Sometimes making something that looks like a casting is half the fun, then you get to machine it as if it were a casting. I've often thought it would be interesting to smelt my own iron. A while back Geezer was looking for some old books about scratch building that included things like making your own motors. There are many levels of scratch building. It would be nice if more people got into it, but not everybody will.