As people might've guessed, I kinda got burnt out trying to set up all of the domain stuff for the continent in advance, described here: How many baronies in a march, etc I was using some scripts and stuff for it, but it wasn't enough.
How do people do it in practice? What do you need to do from the start to have legit domain play as an option should the players want to build domains?
1. Look at the region that the campaign is taking place in. How big is that area? Decide if it's under the control of one ruler, or split between a few.
If under one ruler, is he a sub-realm ruler or an independent realm ruler?
If split between a few, are they all sub-realm rulers of the same larger realm, or of rival realms, or independent realm rulers?
Name each of the sub-realms and independent realms and sketch out some info about their rulers. The size of the realm will tell you his level, title, and income.
If necessary, name and sketch out the greater realm or realms to which the sub-realm(s) belong.
3. Now zoom in on the area immediately around the character's starting location. How big is that area? Decide if it's under the control of one ruler, or split between a few.
If under one ruler, is he a sub-sub-realm ruler below one of the sub-realms you defined earlier, or an independent realm ruler?
If split between a few, are they all sub-sub-realm rulers of the same sub-realm, or of rival sub-realms, or independent realm rulers?
Name each of the sub-sub-realms and independent realms and sketch out some info about their rulers. The size of the realm will tell you his level, title, and income.
To give a practical example, in the Borderlands campaign, when I began play:
I draw a map of the borderlands. It was a principality-sized realm (a "prefecture" in the Auran Empire). I decided it was ruled by the prefect of the Borderlands, who was a sub-ruler to the exarch of Southern Argolle, itself a province of the Auran Empire. I wrote down that the exarch of Southern Argolle ruled from Arganos, while the Auran Emperor ruled from Aura.
I now zoomed in on the fortress of Turos Tem. Since I wanted the fortress to be commanded by a character of about the same level as the Castellan in Keep on the Borderlands, I could have gone with a march or county-sized realm. I went with a county-sized realm (a "legature" in the Auran Empire) and put the legate at 7th level.
Since counts typically report to dukes in the ACKS heirarchy, this meant there had to be a realm above the legate (count) and below the prefect (prince). I decided that the legate would report to the palatine (duke) of Siadanos, to the west.
I then sketched out the size of the legate's realm, which let me guesstime the number of families in the realm, and thus calculate what size military force he could command (2gp / family in the realm via vassal troops).
That's all you need if you just want to get started. From there you can zoom down and build out the vassals below the legate if you want, or cut-and-paste the legate-sized realms to represent other forts on the map, or zoom-up and build out the legate's lord by assuming he has other legate-like vassals.