If I were Putin I would come to conclusion that the only effective defense is nukes targeting NATO assets and population centers, with maybe the occasional bounty posted for high profile targets on the side. The policy could be posted in the form of a simple flow diagram that would be easy enough for the world to understand.
An even better defense would be to leave Ukraine. Putin invaded a country and is now in the middle of war. The nature of war being both sides fight including on both combatants territory.
He wil not use to support his invasion. To do so will force a response. If piting can take what he wants by using a nuke them there is no logical stopping point for him.