This post isnt really about defaults but it is about using command-line switches so this is probably the best thread to put it in since it will avoid having to explain HOW to do it.
For those who are curious about how the AI works (the computer's thinking when its told to play a nation) then the switches of interest are:
-dd
--statfile
--scoreboard
--superhost
--comptrn
Change your icon that calls Dom3 and add these to the command line.
-dd --statfile --scoreboard --superhost
now create a new game (I prefer a really huge map).
Select a nation that can hold out well (I prefer Neifelheim or Jotunheim, or use the Watcher mod)
Add computer players (you can select the setting for one, then hold the "n" key to add all the rest)
Set the game settings. Setting Indepts low will speed up AI expansion
Start the game. Eat lunch or Go to bed.
The SuperHost setting will cause the game to just host over and over and over without waiting for you to do your turn. The --stats switch with superhost will give you a superstats.txt file which will give you information such as the ai-script the nation is running on (aggressive, normal, defensive). The scoreboard switch will give you the scores.html which you can check every so often to see what turn the game has reached and how well everyone in the game is doing.
At any point, kill the game. Remove --superhost and add --comptrn. Now restart the game and do one turn. You now have turn files for EVERY nation in the game including the computer players. You cant do their turn for them but you can see what they are doing.
Contrary to the belief of some, the AI is not mindless.
For more on the subject of watching the AI check out the thread
Curious about Dominions? how the AI thinks? which AI is best/worst?
http://forum.shrapnelgames.com/showthread.php?t=41845