Elemental originally had such promise, however as everyone here is very much aware I am sure, fell far short of that promise in execution.  I just got back on board with Elemental Fallen Enchantress, and have been pretty impressed thus far, but in implimentation I think that now that you have a solid game, there is an opportunity to fulfill some of the original promise with expansion packs designed to bring the world of Elemental alive.

A large part of the promise that the original game had for me, and which I was very disappointed when it veered of this track, was that of the living world.  A world with a number of Kingdom's and Empires fighting each other, but also a world where things are going on independent of what those Kingdoms and/or Empires are doing that impact them, but aren't necessarily triggered by them.  Where a group of adventurers would go into a dungeon, get chased out by something big and scary, and now I as the King/Emperor have to deal with the consequences.  Right now there is a little bit of that with the various monsters and the wildlands concept, but the world really doesn't feel alive to me once expansion ends and the Empire/Kingdom borders meet up, because as the all conquering Empire or Kingdom I can control or easily defeat most creatures that happen to wander into my territory, and there really aren't any non-state actors to worry about or interact with for good or ill. 

So my recommendation for an expansion is the inclusion of non-state actors into the mix.  A party of adventurers that isn't under your control going around exploring dungions and buying things from your cities or selling of their loot.  A trading company that sends caravans back and forth between your cities and your rival's cities (independent of and perhaps in competition with your government sponsored ones).  A thieves guild that attemps to enhance its position in your cities by stealing from you or your merchants and attempts to enhance their earnings by financing bandits within your territory and/or along major trade routes.  This also provides the added benefit of providing additional differentiation between different Kingdom's and Empires by determining how each kingdom or Empire interacts with each NSA type (for example, a certain Empire could levy conscript soldiers from each "landowner estate" that exists within their territory... the cost of that is a potential loss of that estate or lower tax revenue or something of that nature).  See below for a more detailed description of what I am thinking of by type.

Adventurers Band:

Behavior:  These groups of independent adventurers go questing throughout every territory, and can also get involved in quests within your cities and other cities working for one faction (either governmental or non-governmental) or another.  They will generally base out of a specific city, although how far they range from that city will generally depend on adventurer type and level, and as they successfully acquire funds and experience they will gradually expand their presence in a generally beneficial way to you in that city by constructing a building from which they are based and supporting the defense against other alignments.  You may hire these individuals, upon which they become like any other set of hero's that you have, but unless and until that happens these adventurers will pursue their own missions based off of their alignments.  For example, an Empire adventurer band will behave in a generally hostile manner when adventuring in a Kingdom (potentially stealing from that kingdom, attacking trade caravans or disrupting beneficial organizations like trading companies within the kingdom), but act in a generally positive manner in Empires (attacking bandits and creatures, assisting in the defense of cities, accepting contracts from Empire governments, ect).

Economy:  Adventurer's will buy things from your stores, sell things to your stores, and are focused around gaining money, gear, and experience from the environment and from questing both within cities and the countryside.  Improvement will come from adventuring, but each adventuring party can expend money to increase their numbers to replace casualties or expand their size as appropriate, as well as purchase better gear and/or improve their compound/stronghold.

Buildings:  Compound: At a certain level or wealth point adventurers will begin to stop living out of Taverns and request to permission to build an urban compound (quarter tile improvement) in a city that they have been operating out of, or a stronghold in your countryside from which to operate out of.  While voluntary for the player, this will have some pretty decent advantages for them. These structures will also be gradually improved as the adventurer's increase in wealth and experience. First, that compound will provide a one-time payment in guildars to the player for the permission to build it.  Second, the adventuring band will provide gradually improving training opportunities for the players soldiers (so for a cost in guildar's you can send a soldier type supported by the adventuring band to gain experience).  Third, they will assist in the defense of the city if it should come under attack by creatures or opposite alignments, providing a significant defensive benefit.  Finally, the bulk of the purchasing and selling of gear will occur from their base of operations, allowing the owning nation to benefit from the resulting taxes.  The downside of allowing compound construction is that these people are not under your control.  They may adventure in ways that are not to your benefit (especially if they favor a hostile nation of the same alignment more) and could potentially act against your interests within your city proper.

Merchant Companies:

Behavior:  Established with a certain amount of money, these merchant guilds or associations set up trade in between cities, both within and between separate Kingdom's and Empires.  The goal, Kingdom or Empire, is to make as much money as possible as fast as possible.  Kingdom Merchant companies will generally have an easier time setting up trading agreements, but Empire oriented merchant companies will be more willing to resort to less upright means to accomplish their goals.  Hiring bandits to attack rival trade caravans, thieves and adventurers to raid their opponents treasuries and other shady methodology is what can be expected from Empire oriented Merchant Companies.  Finally, a nation state that has a resident merchant company HQ, has a chance each turn to get visibility of a city that the merchant company is present in as an additional bonus to possessing a HQ.

Economy:  Money is their primary resource, generated each time a trade caravan comes into a location based off of size and type (a City will generate more than a conclave or Fortress).  With this money they can further expand their merchant operations (by expanding trading posts or purchasing more caravans), pay taxes (although taxes will discourage merchant companies), hire adventurers or purchase influence for use with nations.  As each Merchant Company gets larger they acquire the ability to sell higher level gear cheaper.  Also, once they get large enough to specialize in a product they acquire the ability to buy and sell resource that they specialize in to states that allow their presence as well (this will always be expensive for balance purposes, but can solve the issue of resource distribution without forcing masses of resources into the world everywhere).

Trading Post:  When a Merchant Company gets permission to set up operations in a Kingdom or Empire population center, it immediately erects a trading post at that location.  This trading post can be expanded by the merchant company with money to provide additional protection to caravans, allow more caravans to exist, improve vault protection (making it harder for other's to steal from them) ect.  The merchant company HQ location will determine its orientation (Empire or Kingdom), and destinctive company altering improvements can be purchased here (these should be either or improvements that change the nature of the company... example being product specialization into metal, horse, warg, crystal trading with corresponding improvements, raw materials and equipment available at all trading posts of that company).  The player, in addition to drawing a tax revenue stream from these companies, also benefits from being able to purchase things from these merchant companies.  The quantity, quality and price depends on the size of the trading post and nature and size of the merchant company.  Potential downsides include merchant competition within your cities and territories (merchant company's can be very unfriendly when it comes to competition with each other) and potentially subversive activities by merchant companies of opposite alignment against both you and your friendly merchants.

Thieves Guild:

Behavior:  Established in both the cities and countryside, thieves guilds make money by.... stealing.  Whether that is from you, caravans, your enemies... well, where there is money there is crime.  Just as long as they get paid.  Now something as large as a thieves guild can't exist without at least an official blind eye, so thieves guilds will seek an official sponsor in the form of one or two friendly Empires or Kingdoms to set up operations.  And from their they will set up hideouts in neighboring territories from which to raid everyone else, including occasionally the empire or Kingdom they are in... especially other non-governmental agencies operating within a sponsoring Empire or Kingdom.  This would, as you would expect, tend to deter trade and lower relations with everyone else.  So why would you allow a thieves guild to set up shop in your territory?  Well, they bring more downside than many other non-state actors, but they also bring many more direct benefits with them.  The stronger the thieves guild in members and money, the more that the HQ provides you.  If you are at war with a nation than that thieves guild HQ can act as a bandit recruitment center, the number and strength being contingent on the size and strength of the thieves guild as a whole.  Brigands will also assist in the defense of this city (since the conquest of the city also results in the destruction of the guild).  You also get a cut of the take, so each time the thieves guild makes money you get a percentage off the top.  Finally, you will occasionally be afforded the opportunity to hire a master thief (read henchmen character) from your thieves guild.

Economy:  Thieves guilds makes money from stealing things.  Destroying caravans and improvements, killing adventuring parties, sending bandits into cities to rob the inhabitants and stealing from other non-state actors forms the revenue stream.  With this money the thieves guild can improve their HQ, hire more thieves/bandits and set up new hideouts from which to spawn thieves and bandits to raid the surrounding countryside. They also pay their sponsoring nation a portion of the take from their robberies.

Buildings:  Thieves Guilds have two building types.  The first is the guild HQ, located in a city where the owner has given them permission to settle.  This building can be upgraded by the thieves guild to provide access to better thieves, and should also have forked development paths that lead to different types of guilds (so one guild may focus on sending thieves into cities to gain money and have units oriented around that, another may focus on countryside brigandry) and so some real destinction between the guild that exists in Resoln vs the guild that the Ironeers allow to settle in their territory.  The second building type is the Guild Hideout.  This building is built in the countryside, and from it brigands/thieves are purchased and spawned to ravage the surrounding countryside.  Difficult to find and heavily defended, these sites improve as the guild HQ improves.

These are the first few ideas that I have had in detail, a few others that I haven't fleshed out yet are landowners, mercenary companies and religious cults/zealots.  I really think that executing something along these lines would really improve that "living feel" of being in a world where things other than Kingdoms and Empires war with each other.. give a true "living" feel to the world of Elemental, but still maintain player control by maintaining choice.  It would also help with the "dilution" of the environment that occures towards the mid to late game as the land is settled and things become much more a contest between nations.  This would mean that the terrain doesn't go away or become less important, only that it changes from environmental terrain to human terrain as these various non-state actors increase in numbers (as the creature life is gradually hunted to extinction).