as farmland was the primary definition of a state's wealth, to have it burned, the peasents slaughtered and buildings destroyed was hugely effective.

Yet, I cannot seem to make it destructible! Is this hard-coded!?

Please help, as this is a fundamental strategy during all wars- denial of resources to the enemy, whether your lands or the enemies.
Of course, if your own lands, you would have to take a huge Authority hit, with a Dread increase, and possibly rebellion of any family members born in the regions affected.

...or is it A Bit much?

Cheers,
HDD