Writing-avoidance activities, series one: Worldbuilding

I am presently tempted to get out the coloured pencils and start drawing maps. So far I've kept rough track of the forest part of Willow Knot with a series of concentric circles that represent one-half day of walking, with the willow cottage at the centre. I fear that once I expand that 'map' to discover where the country borders are, I'll have to revise about half the directions I've been using. The road between the capital cities will almost certainly be reworked.
I've been putting it off, but the coloured pencils are calling me, especially as I get into the 3d section, Myl at court. I'll need some idea how the countries work, how close the cities are, means of travel, and so on.
Which means I need to make important decisions. So far I've thought of the story as set in the Grimm Brothers Maerchen Forest. Boreal forest, foot and horse travel, material culture at late 1700s level. Magic is real, sometimes, but it's the magic that most uneducated people believed in, so there's little adjustment to make. Other times magic is fraud, but frauds and tricksters show up in folktales often enough.
The real countries (France, Germany) may exist, but the action takes place in 'kingdoms' that are more like principalities or duchies, and may be revised into duchies etc. later. As long as I'm dealing with peasants and foresters, I can that vague. (There's a terrific scene in Witchfinder General where Marshall and the soldiers pursuing King Charles reach the coast and find an old man (mending nets?) who doesn't know the king has fled, doesn't know anything about kings or Protectors. Bare sandy beach, grass, and the wind blowing over their voices. It's as if they've reached the edge of the world.)
But once the story reaches the court, the situation has to be firmed up. I need names and maps. I can approach this a few different ways.
(Pause to strongly recommend Wrede on Worldbuilding)

1. make up a fantasy world. I really don't want to do this. Really, really, really. I don't know enough about geology, geography, politics and logistics to even start. I suck at invention.
2. alternate history. Take the map as it stood at the turn of the century, change the names of all the countries and fiddle the borders a bit. I think Guy Gavriel Kay approaches it that way.
3. go the Ruritanian / Graustarkian route and just fiddle the borders to squish a few small countries in amongst the big ones, maybe in disputed territories like Alsace-Lorraine. Caroline Stevermer did that in College of Magics, I think. I don't count it as alternate history (though I suppose it is) because the trick predates the category.
   

Obviously I now have to find old maps of Europe, and books on the history of mapmaking. Obviously.
I'll need a rough map of the forest and the marsh, showing the road, the robbers' den, the willow cottage and the edge of Midame's lands. I'll need a floor plan for the palace for the 3d part. I may need a layout of the capital city, but I'll probably steal that fairly directly from a city map of the appropriate time and appropriate landscape, if I can figure out those out.
Maybe I'll do that in the evenings, instead of reading FandomWank.

Another thought experiment: If your book were published, and acquired not only readers but fans, what sort of fanfiction can you imagine being written from it? How might you feel about characters being revised, and which characters or situations do you think might be more susceptible to revision?

The answer to yesterday's question is: Wait one or two days. If the swelling etc. just stops, it was the arthritis. My knee is almost normal today, which seems unlikely if it had really been injured.
Nice to have that figured out.