Battle Brothers update 1.0.0.4 introduces the option "Permanent Destruction" during the end game crisis:

Changelog

• Added map seed that can be entered upon starting a new campaign, and seen for ongoing campaigns created after this update, for replaying and sharing maps.
• Added checkbox for 'Permanent Destruction' during late game crises when starting a new campaign. It's checked by default to work how you're used to. Unchecking it will result in settlements getting the 'Razed' situation for a considerable time instead of being permanently destroyed.
• Added warning prompt for users of Avast due to compatibility issues introduced with one of their latest updates.
• Changed game to unpause only after autosaving is completed when leaving towns in ironman mode, so no time on the worldmap is wasted.
• Fixed issue with the game potentially hanging in some cases as characters rise from the dead during the Undead Scourge.
• Fixed AI not using the 'Footwork' skill properly in some cases.
• Fixed issue with 'Decisive Battle' contract.
• Fixed issue with 'Privateering' contract.
• Fixed various minor issues.