Detailed and more advanced stuff here. I underlined the major questions.
Industrial production philosophy
The main concept about production is that each steel foundry takes 1 cool and 1 iron and produces 1 steel. Always. No exceptions (it makes the interface look much better, no ugly fractions and the most important part, industrial production is strightforward and not confusing).
But I need to take into account labour availability, their education (public education was originally not invented for making more scientists but to teach workers alphabet so they can read instructions and do some absolutely minimal math).
So I thought of wages system. Factory can operate at full capacity even if there is a serious shortage of workers but you would need to pay them mych more. If there is enough workers you per $1 per worker, if there is shortage you pay $2 TO ALL workers in that province, if there is twice less workers than needed you pey $3 per worker and so on. When it reach tripple workers shortage the building interface gets grayed out and you ca't build anything more untill more workers arrive to the province.
But how about education/literacy? How this could affect/be connected to production?
There would be 2 buildings, shool and university. But the university would not be "a better school", it would have a slightly different purpose. There would be 3 levels of education (Basic, Advanced, Expert). In school they would teach Basic for 100 people and Advanced for 20 people. In universities Advanced for 10 people and Expert for 20 people.
The Basic is used by industry (barely literate workers, just so they can operate machines better). It does not affect science at all.
The Advanced is used by government administration (better efficiency) and for science (small boost).
The Expert is used for science (huge boost).
I think education levels should be country wide, non province wide (the educated population would be assumed to always be in the place they are needed the most). But I'm not sure about that one...
The effect of building a school would not be instant. It would teach (Basic level) +5 people per turn up to 100 people total. So if you have 100 people in your country it would take 20 turns for all of them to reach Basic level.
Note that at some point you would reach 100% of Basic education yet you still might want to build more school for Advanced education (which would be 20% at that point). The university is an option too (if you ant Advanced), still, it's less economical than school (university is more expensive and teach half Advnced compared to school), but on the other hand it also adds Expert, which is a nice perk not granted by schools... It should lead to some non trivial decisions if you should build schools or universities.
Administration (local government) and paper
Each provinced has a level of local government (local administration, tax collectors, courts, etc). At the start you have a level 5 in your capital and level 0 in all other provinces. You can upgrade it with one click on the province screen (relatively expensive). One one hand it would work as a lock (to not get the player overwhelmed and discourage improving all provinces at once), in order to build any industry you need administration level 1. Upgrade is not cheap, and what's worse require upkeep each turn (so you would go bankrupt by improving all provinces at the very start). On the other it would increase tax collection effectiveness, and possibly other goodies.
I think it would be very cool to introduce paper as upkeep cost for administration You start as a primitive agrarian country and them improve your government and need to build more and more paper mills producing more and more paper eaten by the ever growing bureaucracy Or maybe you could intouduce edicts/policies, and each of these would have a turn upkeep paper cost as lang as in effect. Quite thematic and realistic I would say.
I think paper should be used as upkeep for schools/universities somehow. Maybe halve the efficiency of these by half if no paper upkeep is paid? Or maybe increase the cost of running these? Or maybe auto import paper upon any kind of shortage?
Export and consumer goods
You should be able to sell finished goods to some other (virtual and not present on the map) nations. Or maybe sell these to your population? I'm not sure how make that part. What I know is I don't want to fully simulate all kind of AI competitive empires, I would love to keep it very simple somehow (beacuse the game is focused on internal development of ones country)...
Sphere of influence (AKA ruling the seas)
There should be a concept of having navy fleet (to protect your merchants, making sure you are the one who get the profits from trading with primitive nations). Again, I have not thought how to handle this, would like ideas.