Well ... I think the ideas of "Global Economy" and "Resource Sites" should first be separated for this thread to continue.
Global Economy ... each city in the world has the POTENTIAL to access your supply of resources.
Resource Sites ... large amounts of resources are granted by specific locations, as opposed to buildings.
I still support a "Global Economy" ... although I think cities should only have access to metal if they have a "smelter" building + road to a city with Metal within its Influence, or simply metal within its Influence. (as an example)
I'd prefer a hybrid of Resource Sites and a Creative Assembly style economy. (by Creative Assembly I mean like the Total War series ... but really not just the Total War series, but MASTER OF MAGIC also has a similar economy).
In this system ... the buildings you build affect your economy (the most??), while special resources like gold/etc have a HUGE EFFECT early in the game, and less-so later on.
Basically, where you build your city has some effects on how effective its production will be ... perhaps you could have certain features produce vectors? which stretch outwards giving bonuses to tiles along the path, slowly diminishing in returns.
Thereby ... Cities close to a few forest tiles will have a slight materials boost. Cities close to many forest tiles will have a large materials boost.
Cities close to a few grassland tiles will have a slight food boost. Cities close to many grassland tiles will have a large food boost.
River tiles could have an effect on both food and gold.
Basically, any swamp or desert tiles near your city will make it less effective because you are not receiving any food or materials boost that you would otherwise receive.
Of course, Resource sites could (and probably should) still be in effect, and still directly contribute to the nearest city whose influence covers it, and still be very important.
Now ... perhaps resource sites should give such "large advantages" ... (much more-so than the crappy advantages Gems or Gold Deposits gave on MoM)
Still, I think another thing that could improve Elemental's economy is a taxable population with a population happiness. (obviously NOT large enough to be able to simply pay for the entire game on taxes alone)
Now ... happiness could have several factors, in Elemental the population doesn't produce any resources (like food, materials, etc) .. but if they were taxable they could *at least* produce gold, or knowledge, or magic.
Now .. citizens (maybe 1 "face" per 200 people), would be taxable if happy, and non-taxable if not happy. Also, unhappy faces would be more likely to spawn angry/chaotic NPCs ... as well as bandits and rebels.
Basically, if you have low taxes, you'll get low amounts of gold per pop, and happy cities with no unrest.
If you have high taxes, you'll get high amounts of gold per pop, and many bandits and chaotic NPCs ... plus the possibility for Rebels spawning, as well as the possibility for a City to defect.
(A City will only defect if an uncontrolled Chaotic NPC or a controlled Champion with low loyalty is stationed in a city with more unhappy faces than happy faces) ... also, a City will still not defect if there happens to be a High Loyalty Champion is present within a city, even if unloyal heroes are present.
However ... if there are Chaotic and unloyal elements near a very unhappy city, rebel forces will form outside the city walls, and those Chaotic or unloyal elements will abandon your empire and join/lead those forces. So if you have a Chaotic NPC, a low loyalty Champ that you own, and a high loyalty champ that you own ... all stationed in a very unhappy city, then the high loyalty champ and most of your army will stay in the city ... though the other two Heroes will leave and form an army mostly consisting of Rebels (city population) and some of your stationed military. Plus some bandits and savages from the wild.
So basically ... part of your army will leave, low loyalty champions will leave, Chaotic NPCs will actively turn against you, Rebel forces will begin to spawn ... and all of these will team up with each other, and bandits, and attempt to take your cities.
So then, if a city defects, or if it has been captured by a Rebel Army ... it is controlled by a Faction of Rebels (psuedo-Minor Nation) who is controlled by the strongest Chaotic Champion that joins the cause (so the leadership may switch hands several times).
Rebel factions are automatically at war with all factions, but if the leading NPC has good relations with any faction, they can declare peace to become "recognized as a nation".
Anyways, these rebel cities will continue to produce rebel troops, and lead their armies against your cities ... until you declare peace and "recognize them" as a nation. Of course, there is a slim chance that they may not accept your peace ... but that would only be in the bloodiest civil wars, or if the Rebel faction is led by one of the most ambitious NPC AIs.
//
So as a recap summary ... surrounding terrain = loose bonuses on the economy of a city (not directly tied like Civ was)
resource sites are important ... high pop cities with good buildings become more important (but are still more effective WITH complimentary resource sites)
taxable population (for gold, knowledge, and magic)
population happiness (no unrest -> bandits -> Chaotic NPCs -> rebels -> Civil War)