Time will tell whether SBS go down LIFs path of controlling hostilities. Hostiles also make up the population and while they frustrate us, they give us a reason to invest in our defences and work together with the defenders of the realm.
The PVPers need an outlet and the freedom to do what they want with their only restrictions being how the defenders prevent it, fight back, outsmart them, etc. Not game mechanics.
Trust those who are victims of hostilities be forced to think of ways to stop it or make themselves a less attractive target.
Concerns the nerfarious may start fires will encourage Mayors to build more wells around the town. To invest in stone instead of wood or seek the services of those who have researched flammable proof wood.
Concerns the nerfarious will spread disease encourages Mayors to control their trade ensuring they are informed of plagued communities they're trading with, ensuring they have the medicines in stock, etc.
If caught, the nerfarious can be locked up for life. Which is a very big deterrent that reduces the number of "griefers".
By not allowing these opportunities to "grief" there's no need to be as creative to defend your people against outside threats. Ideally, nobles rise and fall but only the smartest and most cunning will continue to rise. Game designers musn't assist the less capable and the incompetent.