TL;DR: I could include coke (when DF2014 becomes stable enough to update this), but it would at least have to be handicapped, with more effort to make it than charcoal in pure form, and/or more refining steps for the metal, and/or weaker steel versions.
Long version:
I believe this only applies to unrefined coal.
Contemporary sources I found as well as the first half dozen secondary sources all attest to a significant difference between COKE and charcoal, differences that mattered for metalworking.
First of all, coke requires vastly higher temperatures to make than charcoal. You're looking at around 1800 degrees F, versus more like 500-600. So one requires a furnace, while the other requires a big pile of dirt and wood and one dude watching several dumptruck-fulls during the process. Charcoal is much cheaper and less labor-intensive to make, so at the very least, if you want to equate the two as fuels, it would only be fair to make coke much harder to make in-game by comparison. If you don't use intense external heat supply, you get still
more chemical impurity differences between the two (see next paragraph):
Secondly, neither charcoal nor coke are pure carbon, and are not chemically interchangeable. They are carbon + whatever was in the original material that is refractory and non-volatile, which occurs in the tens of percents, not trace amounts. In the case of charcoal, this is a small amount of ash consisting of almost entirely of silicon and calcium and potassium ions. In the case of coke, this is a different composition. There is much more silicon (which is bad - it makes the steel larger grained and harder to work for forging and weaker in overly high amounts.) and sulphur and phosphorus in much larger amounts as well, which embrittle the steel. In either case, source material matters, but with wood, there is almost always more variety to optimize from (lots of species of trees nearby) versus typically once homogenous source of coal locally.
Historically, you can see that everybody everywhere converted to coke for iron
only after charcoal became too rare or expensive locally. The final product is either inferior, or requires a number of extra explicit purification steps that are expensive and time consuming.
At best, in the mod, I could add two production branches - an easier, higher quality charcoal route, or a coke route that has more processing steps and fuel and/or weaker steel.
Raw bituminous coal can and is used for blacksmithing (I've done it IRL).
Notice that my mod does not require charcoal for the forge building. Thus, it does already allow a wider latitude of fuels for blacksmithing. Blacksmithing is quite different than smelting, even bloom smelting.
The way I understand it, the only difference between blast furnaces and bloomeries is that the blast furnace is bigger and hotter, thus melting the iron, requiring flux and allowing continuous operation instead of batch processing.
And it uses chromatography for separation instead of physical pounding out.
And in order to get to the hotter temperatures, it requires more oxygen, which also changes the chemistry around.
And it requires extra steps insofar as pig iron is useless by itself and requires fining forges etc, whereas bloomery iron is workable directly.
In addition to the differences you mentioned, it's actually quite different.
And yes, dwarves might have had access to it, being dwarves and whatever. I actually included it at first, but in play testing, it was less fun, because it was just almost impossible to strike a realistic and interesting balance between the two methods. Blast furnaces had to be more efficient if/when you had flux, otherwise what's the point. And yet this was difficult to accomplish in dwarf terms what with the extra steps and the lack of an ability to actually mod continuous processing, etc.
It ended up being either only marginally better and boring, or bloomeries had to be too inefficient and frustrating on non flux maps to be fun. *shrug*
This looks really cool. If no one minds I think I'll port it to Rubble and extend it a little (I like lots of alloys, so a few unrealistic things are just fine by me :p)
With some sort of credit, sure.