hope i'm not jumping in here to late ,but I posted a bunch of brainstorms on this bout a year ago and have some sujestions
there has been the subject of "growing hourses and elephants for millitary .
could this be expanded to "power" resources in the early ages such as oxen llamma otherwise known as beast of burden and these rescources used as such in the production of improvements and wonders in conjuction with hammers.
i know that many people here dont like the concept of growing food rescources ,but i see it as a necesary ,if you consider the fact it takes a large amount of food to fuel armies ,and to be honest if it wasnt for the midwest bread basket the second world war might have gone very differently.
i think perhaps additional basic tiles might help in this ,along with grasslands additional grassland tiles could be created such as temperate grasslands, tropical grasslands ,artic grasslands ,river basin grasslands ,certain crops could be grown to spacific types of grasslands in this way it would limit growth of crops .The other thought is should these crops be planted or should they grow automaticly if that crop is being used as a food source with in the city.
the availability of crops being accesable to diferent types of grasslands could be opened up as tecnology increases.
plains perhaps could be used to grow livestock.
On the collection of rescources if within the city production speed is based on population and worker capacity then why not expand that to the collection.
stacking workers on a tile should increase the amount that is being collected of a resource, if a worker is collecting iron from an iron mine then 2 workers stacked on that mine should increase. This could also be technologicly limited.
acces to rescources , one thing that has bothered me is there no such thing as a trade road ,shipping lanes ,port towns ,etc.
My thinking is there should be a limit on how much rescource can be transported on a road or port .building on top of that road or port would increase the volume of goods that could be transported.This could be balanced out with a maintance cost associated with trade infistructure.
A level one road could transport 8 rescources while a level 2 would allow 16 rescources.This could be aplied to ports as well.
on the subject of luxeries I think that alot of the natural luxerie rescources as well as some of the "growing" rescources could be brought in to the cities and create industries based on luxeries..Textile industries ,this could bring in different types of rescources ,such as cotton ,silk ,flax ,etc and create additional types of luxery rescources by way of textile mills. same could be said of distilleries ,certain types of agricultural resources could be brought in to produce alcohol rescources.
On the subject of trade ,why not have a general pool that exces resources go to and you simply set the selling price,It is purchased on the international open market at the lowest bidder .this should be easy for the AI to understand.