To address your previous comment, the only thing that the real count for Iron/Steel should practically prevent is taking Iron or Steel from Warrington station.
If we look at the design of Trainmaster in general, small amounts of cargo are needed at many industries all throughout the map. For example the Machinery needed to make Glass (1920 onwards). So, in practice we could see at least a dozen cities on a TM map where just letting the train run on "Any Cargo" consist will disrupt reliable production.
If you see Gumboots' acronym "HAB", that's short for "Haul Anything But." This is a "wish-list" feature that many of us wish the game could do. So we would say that in Warrington station the train shouldn't pick-up any Iron or Steel. Or at the 20th century town with a Glass Factory it shouldn't pick up any Machinery or Chemicals. But it could pickup anything else (that will make a profit). Unfortunately such a feature does not exist.
In 1.05 custom consists are for-profit. Without HAAL we could do this:
In 1.06 and TM, the HAAL coding "hi-jacked" the custom consist setup. If we used the above consist, the train will haul that cargo no matter what, without considering profit. In the case of supplying industries, we don't care if the train is running at a loss (as you said this was what HAAL was intended for). But it disrupts the normal profits from distribution of consumer products, like Food, Goods, Furniture, etc.
So how do we manage these things in TM? The following is the philosophy I have developed. It may not fit with all play-styles.
In the 19th century there is a lot express in TM, including Troops. Lean into this. Most connections are worthwhile if you only run trains set to "Any Express."
TM is all about industry. In the 20th century, especially mid- to late, lean into industries. Industry revenues are high.
Think about cities individually. In a 19th century game I have probably "express" connected all the map. That means I connected the cities for the express revenue. I will just use "Any Cargo" trains for this initially. Later when I am starting some industries up, I will add a prefix to the station name for example "=Crewe" to denote that trains stopping there should pickup express only. At the same time I will update the train roster for express only orders at the trains visiting that station. It's important to keep trains organized to find them easily. I just renumber them so that trains on the same route are consecutively in the list. (See this topic on that: https://hawkdawg.com/forums/viewtopic.php?f=5&t=4133) The freight trains are generally specific.
I build small stations for deposit of resources to industries/ports. The main station is for pick-up. The purpose of these is to drop the cargo on the correct economic cell to feed the industry directly.
How to run distribution of consumer cargoes from these cities?
If resources are plentiful and we don't mind wasting a few we could set some our trains with a custom consist like this:
Something that will also make a big difference (if you can build industries) is pairing similar industries on the same economic cell. As an example: Oil Refinery/Plastic Plant, Or Electronics/Machinery Plant. Building on the same cell as a resource and especially the agricultural communities which have multiple outputs cuts down on haulage needed. For example Paper Mill/Cereal Company pairing.
About Warrington Wire:
My memory is a bit hazy, but I think the GV4=1 event is for the express haulage share your company has versus the AI. It should be (Loads of Express you hauled/Total Express hauled by all companies) in the current year. Maybe there is some error that I didn't catch when testing the scenario. Can you describe in a bit more detail what is happening?
FYI, I felt that the original scenario was a bit boring in the end-game. You setup your Iron/Steel haulage, then you were sitting and waiting to gather the needed points. When fixing the coding errors I also took the liberty to add the express haulage share and industrial profit elements. The hope was that the player wont get bored later in the game.
PS. Here's a patched Meat Packing Plant to go with the files I already shared. The Hides recipe had a mistake: input amount one byte off. It would make Hides even if it wasn't supplied with any Livestock! I thought I had fixed this previously and shared it, but I can't see where now. Here's one I did:
but it's fairly crude way of handling industry supply, and as pointed out the supplied cargoes will tend to drift away unless you use other techniques as well. If you do use the other known techniques, you usually don't need HAAL. Then there's the problem it creates with price islands and exploiting them, which led to those being disabled in 1.06, which led to other problems.
But again, it requires compromise. The game's limitations mean it's impossible to create truly accurate valve gear.