Talked with Rob a bit more today; discussed a few interesting points. All of the following is likely to be mostly accurate, but is doubly uncertain because I'm speaking from memory and because nothing is final until it appears in the comic proper.
Farms aren't popped by people, except possibly by a three-caster link with thinkamancer/florist/dirtamancer; there are instead "farm sites" just like city sites, which can be upgraded (0-level is no farm, level costs and number of levels are not the same as cities) and then will automatically link to the nearest friendly city. That is, if Gobwin Knob was razed, the rations currently being produced by its farms would simply pop in whatever the next closest city held by the side is. Because of this mechanic, farm sites do not have to be anywhere near cities, because they can link to them over potentially vast distances.
However, some units have a "farming" special, which is a natural dirtamancy/flower power thing that lets them cause rations to grow and subsequently pop as long as they spend their turns "farming" (no movement) in a hex of the appropriate terrain type. In the event that a farm site is razed (presumably by an enemy side), building it back up requires a unit with this special, or an appropriate caster (florist or dirtamancer).
"Mines" are done in a manner resembling the farming special, rather than the farm sites. That is, certain hexes of certain terrain types have mine-able resources, and a unit with the digging special (or a dirtamancer) can spend their turn "mining" with no movement in exchange for a random chance at getting gems. Gobwin Knob's mines are a result of hundreds of turns of this being done on a large scale, so this can semi-permanently alter terrain.
Semi-permanently because terrain which is altered by units' actions will gradually revert to a natural state over many turns; this is a form of Signamancy, in that absent any unit action, a hex's signamancy will gradually drift so that it looks uninhabited, just like units' signamancy will gradually drift to show truths about them. Interestingly, this means that signamancy is used for tracking- the Signs left by the passage of a unit (appearing as broken branches and such, like real-world signs of passage) can be read, potentially even many turns later, until the hex has fully reverted to its state prior to their arrival. When you bring natural magical abilities or casters using Signamancy into the mix, tracking becomes proportionately more effective.
Books are a form of Signamancy, because they are by their very nature information represented physically, which is what signamancy is all about. Libraries in cities normally automatically update by natural magic only when the city is built/upgraded, but if you have a Signamancer they can bring them up to date (recall that Parson said libraries have old battle records, etc. for referencing). Presumably this applies to naturally popped maps and such as well, as they are also physical representations of information, and thus Signs by nature.
Libraries in every capital, or possibly every city, naturally pop with a complete copy of the Titans' Scripture. It is identical in all instances. Because everyone is working from exactly the same base information, all religious conflicts are based upon differences of interpretation- or more likely, practical reasons being masked by religious ones.
Managing a city requires the entire turn of the unit doing it- meaning that they can use no Move and cannot engage other units until their next turn. This means, in turn, that if you raid a city and the warlord who managed it engages the raiders, even by something like lending their leadership bonus to an archery stack to make them more effective, the management bonus is lost. Obviously, this makes courtiers somewhat more important- because it lets you actually use your warlords for defense while keeping your bonus, because you can keep a noncombat unit safe.
I remember something about promoting courtiers into warlords, but can't recall the details. Unit barriers in general seem significantly more fluid than we've been treating them as, or at least that was the impression that I got. Knights apparently have enough intelligence/initiative to use their own discretion when presented with an enemy in the absence of a warlord; they are treated as self-led and can choose to engage or take other actions instead of auto-engaging. Possibly, they also provide themselves (and only themselves) with a leadership-type bonus based upon level, and there might be some kind of entourage bonus if they're stacked with a warlord; details are sketchy and explicitly requiring more thought from the Titans before being nailed down, but it's something for us to think about and come to our own conclusion on in our games, of course.
I am probably forgetting a few things. The conversation sort of drifted around, and I kept pulling back to allow for commerce. Forgot to ask about upkeep on caster-created units, unfortunately. Perhaps next year.