Expansion already and we haven't even gotten the original up and running without bugs. Maybe you should have waited a few more months before releasing the WoM and just put out Elemental: Fallen Enchantress. I really hope you fix a few things with this expansion....
1. Fix the Out of Memory crashes. Really annoying.
2. More detailed and rewarding quests.
3. A more diverse tech / spell trees to give flavor to individual factions. Right now you only need play one Kindom and one Fallen to get all of the feel for the game.
4. More diverse and thought out NPCs with possible side quests: You pick up an NPC looking for her twin brother. In your travels you find <trigger marker> if NPC is part of faction, then, You find a clue to her twin brother's fate... Chain quest with possible out comes: a. brother joins faction, b. brother is found dead but puts and end to her search, c. brother has turned evil/good fight. Another idea, Paladin or anti-paladin, joins faction but has lost his war mount, armor and weapon. Side quests to recover them all. The options here are limitless and can be done with very little coding. NPCs should not respawn as well. Once dead they are gone (unless Life Magic: ressurect or Death Magic: Undead). Mulitple spawns of the same NPC is not only annoying it can unbalance the game if you get say 10 tech related NPCs of the same name/same person.
5. A larger selections of abilities and traits to flesh out unique factions. Minor Factions should be there as well (actually spawn during a game..not currently happening as they are on placed on game maps) to provide flavor and distractions for expansion. Each minor faction should have it's own ZOC with resources and growing city. Prevent growth by not allowing them to make pioneers.
6. Armor/weapons. More detailed and diverse armor. 2-3 forms of leather, Cloth armor for casters, 2-3 mail/scale types, 2-3 plate types. Weapons should be more readily available. Broadswords after several tech advances? If they still know how to make blades then swords should be a low tech and advanced metallurgy gives you better/stronger blades.
7. Spells. Make some spells (spell books) prevent others from being learned so you have to choose your destiny. Don't make Fire the win all with it damage. Damage spells shouldn't be the major difference between them. Firebolt, Icebolt, Stonethrow, they should all be close to the same and some things would be immune to them, ie Fire Elemental is immune to (yep that is right) Fire! The diversity should come from functional spells. Like Earth would give you Farming Bonuses, Water: ships bonuses, Fire: ravaging land tiles, Life: healing spells, Death: (yep) Death spells. etc. This would make you have to choose your type of ethos or style and NPCs would only join you if they had the same ethos or closely related to prevent NPC armies with 6-10 spell casters.
8. Resources should spawn more logically. I can tell you how many games I played where ore or another resource spawned in really wierd environment tiles. Also more diverse resources and mounts
9. There should be more mounts that are also researchable, ie standard horse, scouting horse (speed), War horse (bonus fighting/armored), etc.
10. Finally, units should be more useful. I don't even created units in most of my games. I just buy up every NPC I see, Imbue them, and arm them and beat the snot out of other guys armies. They should start out in small squads. This would make them more deadly early on. As Bruce Lee said. (paraphrased) "I can fight one person no problem, 2 would be tough, but 3 or more would be almost impossible." Numbers kill. A knight in armor on his war horse is attacked by a mob of 10 spear wielding militia is gonna die. Sure he is gonna kill a lot of them but he can defend himself from all directions all at once.
I just hope you put more time and energy into this expansion because I have had to rewrite so much of your code to make the game enjoyable to me I might as well make my own game. I don't want to do that. That is what I pay you for, and yes I do, because I buy the game. You have such a good concept here if you just took the time to flesh it out. Make it something it was supposed to be. At worst, dumb it all down and make an electronic board game of it. That way no one will expect more from the game, but if you really listen to your buyers, maybe you can give them something they want. Just some of my thoughts for what they are worth. (probably not much as many will flame this.) Good luck. I will play the expansion as I get it for free but if it is like the original, I won't bother even downloading my second free expansion because I will be done buying or playing Stardock game.