If I can like to add "Depends of nearby Town Population" to all Industries, even Mines. Some farms too especially those that harvest crops.
I am not sure this is a good idea - some diversity is always good, especialy in multiplayer environment, where in most typical case a session lasts for couple of hours only and supplying primary industries is usualy the best way for a good company start.
I like to add some small Industries that build within or close to a town that you would find in towns. Your idea has some prospects too.
The weirdest idea just came to my twisted mind - what if some of those town based industries produced just trash, waste? Then it would be forced onto your stations, it would be bad for all ratings and you'd have to transport it to a garbage dump industry somewhere. In citybuilder mode you'd be require to transport it out of town to allow it to grow. In later years a recycling plant could join the chain too. I imagine it's not going to be possible to code, is it? I am just dropping ideas, sometimes I go wild =D
Maybe combine Manufacturing Supplies and Engineering Supplies together and just call it Supplies.
Let's not make anything simpler, if possible =)
And make Grain and Wheat as separate cargos like I did before. Maybe have Wheat and maybe Cereal Crops.
If I can make a longer chain of cargos from the raw material to the finish product.
Sheep farms thinking of changing these to no longer produce Wool .. instead take the sheep to a Shearing Shed and produce the Wool. Sheep farms in Australia usually produce Livestock Wool and Grains (Wheat, Barley, Oats). So if sheep go to Wool sheds, Sheep farms can then produce Livestock and Grain.
MILK it real it goes from dairy Farm to a Dairy where it is bottled and make into other dairy produces before heading to shops. At moment it is changed to FOOD. So like to change this to something like Dairy Produce and take to a shop ina town and from here it changes to Food.
More complexity and realism is always welcome.
Here's another wild idea: I'd love to have infrastructure construction requiring resources as well as money. Rails would need wood and metal and gravel, roads - sand, gravel and asphalt, stations - metal, stone and building materials. Each company would start with some amount, kinda like you do in Age of Empires meh nvm =D I've let myself go too far =D
I friend of mine has this saying he likes to bring up often:
Small people talk about others - medicore people talk about facts and history - great people talk about ideas!
Ima go with that as an excuse for wild =)