I've done a lot to make the game harder, using INNs as the AI's free 200% farming income building that I simply don't use. (this means no mercenaries of course as well).

That and making trade worse and giving 100% import income.. and other stuff.

Now I wonder, would it be possible to use the land clearance building as the Castle building in the main campaign, or would that only be available in the Viking campaign?

If it were possible to make castles not get sacked, this would be really nice.