Though the title of this post shortchanges the role An Echo, Resounding is playing in my development of the referee rules in my campaign, I figured it was best to stay consistent.
As an example of the role AER is playing, though I'm working my way up to the domain rules, rather than down, I am broadly using the categories and concepts from AER's domain play, so that most of the framework for reconciling Dungeon World style GMing tools with the AER domain play should already be there. So, last night I figured out how I want to work steadings (which include cities, towns, and keeps), ruins, resources, and assets.
The inspiration I stumbled upon was that Gangs in Apocalypse world already provide an example of the intersection of statted out groups with the GM organization tool of Fronts and Threats. Dremmer's biker gang is a "threat" when it comes to figuring out what things are happening off stage and how they will react to player actions and/or threaten things the players care about, but when they throw down in a shoot out, they are a "gang".
So, by way of comparison, in Fellhold, there might be a bandit group that is written up as a threat to help me keep track of them as elements of the world, but if that bandit group starts threatening a domain's trade in a significant way, they'll be statted up as an asset that can move around and interact with other assets at a domain level. If it comes to personal combat, the existing D&D rules (well, Swords & Wizardry WhiteBox, as modified) will come into play as per usual.
I intend for assets to be able to exist for all three domain values: military, social, and wealth. Assets of different types will have different explanatory tags (for example, a social asset like a town council, won't likely have a damage/harm value, nor will it be mobile). But all assets will have a type tag (military, social, or wealth) and a size tag (the amount it adds to the listed value for the steading that owns it, or the amount it possesses on its own).
Assets are basically a way to enable increased granularity than the DW steading rules. They don't supersede them, they just supplement them. So, a Defense value of "Militia (1)" implies that the citizens of the village can be organize somewhat effectively with some real weapons, and it's given as a characteristic of the Village. On the other hand, let's say that we have a big city that wants to detach a small unit to go attack a neighboring town. Its overall Defenses might be "Legion (6)", but the referee decides that its important to keep track of how that military might is dispersed, and so creates an asset to represent the detachment sent away and gives it a value of "Watch (2)" and then assigns it various descriptive tags. At this point it become an asset of type Military with a size of 2. The city's defenses go down to "Garrison (4)" until the asset returns or enough time passes to replace it.
By default, assets should only be prepared for things that have enough of an independent existence to matter (like a powerful merchant guild) or are likely to be dealt with separately from the town as a whole (so, for a big city, you don't need to make an asset for the watch, the garrison, and every unit of the standing army unless and until they become important to game play).
Likewise, groups of monsters can be statted up as assets that live in Ruins or Resources, but this is only necessary if Domains take Domain level action against them, or if you want them to take domain level actions. So, that tribe of Trollkin squatting in the abandoned gold mine can just be written up as a threat as usual if the players are coming to root them out personally with sword and torch, but if a player owns a small domain and sends his troops to deal with the matter, then the goblins will need to be statted up as an asset so they can interact with the domain level troops action.
While I toyed with the idea that Ruin and Resource locations would have monstery/wild versions of population, wealth, and military, I decided that it was a bit forced and hindered the flexibility of threats and fronts. Instead, Ruins will mostly be collections of descriptive tags and associated assets. All Ruins will have a Treasure tag which is like wealth, but finite. So, if adventurers recover 1 Wealth worth of treasure from a Ruin that started with 3 treasure, it now only has 2 unless more is brought in. I probably need to figure out a good conversion from actual gold amounts to treasure, but that's difficult since 1 wealth is supposed to be enough for a small village to get by on. There may be some scaling issues involved, but we'll see.
Resources will also be pretty minimal. All resources will have a "Type" tag that describes what they are, and a "Size" tag that represents the amount of wealth that resource adds to a steading that owns it. A size of 1 will be typical, whereas 2 represents a truly noteworthy reserve, and 3 would be a once in a world source of a resource (something like South Africa is for diamonds). Like Ruins, Resources can have threat and other descriptive tags to make them more than just a place on the map that makes other steadings richer, and they can "house" assets.
At this point, I'm pretty happy with the structure of how tags will work with the categories I got from AER, but I need to dive into AER's methods of generating Ruins, Lairs, Cities, and Towns in order to write more tags and new threat types with new instincts and moves. After that I'll look at Domain Actions in more detail and and combine it with DW's "Updating the Campaign Map" to finalize the domain level rules.