The initial EWOM will be fairly limited to 12 human races.  I want to play a bear race or get some bear Calvary sometime in future mod/expansion; I try to outline a mechanism that fun & implementable in day 1 of EWOM.

Bear is a race.  It is customizable by players in SDs’ Bestiary.  Its major difference with the default races is Bear’s Settler built a Den & the den has to be built in a forest, low hills, and mountain, underground tile (no plains, no dessert etc). 

When playing against the Bear, we play against them as just another AI player.  There is no major/minor concept as in GalCiv2.  If the map has 90% forest but little plains, the bears are the force to reckon with; the Fallen & the Humans will struggle

Bear’s den will function as normal cities. Assuming any barrack structure can produce Spartan, you’ll get the Bear Spartan there.  There should be unique structure for the bear race too. 

If the den is captured by a Human/Fallen player A, A cannot produce the Bear Settler, or build any new structure inside.  Player A can still produce new (bear) units that it originally is capable of, but its production rate will be decreased to 10% to 50% (depend on balance/play test etc).  The same applies, if the Bear player captures a Human city.   Incompatible player is INCAPABLE to use the city to its full capability, because their settler cannot settle to this particular land tile.

The Bear (AI) player will have the same diplomacy options/capacity as others.  They even have their Victory condition.  However, their initial diplomacy strategy will be extreme.  In turn 1, the beast race maybe at war with everyone (think your typical barbarian).  Or it is defaulted to non-aggression to all Fallen/Evil players & war with all Human/Good players if it is the Goblin race.

Random barbarian roaming stack, is NOT an AI Player.  However, if a randomly generated stack happens to contain a settler unit, it can become a new AI player when settled.  Also there should be some kind of unit called “Supplies” allowing rushed build of structures, so a new AI player will not be too weak when the game is well into its 200 turn.

The same concept applies to other races/player..
1)    Demons builds castle on lava, hell, on top of plan, grassland etc
2)    Undead builds their tomb on graveyard, swamp, any underground, on top of plan, grassland etc
3)    Giants builds their den on forest, low hills, low hills, mountain, underground (i.e. compete with bears’ habitat, can settle on a razed bear den, migrate a bear den to Giant's den etc)
4)    Mermaid builds their palaces in the ocean
This mechanism should opens up tons of possibility!