Use <magic material> to build a wall around the city? Have the people who maintained each individual building form a team that can keep an eye on sections in shifts? If we have enough magic material, build a double wall system for breaches?
> Use <magic material> to build a wall around the city?
That sounds expensive. Do we need to do that? Does it solve the problem better? Does it maybe create a worse solution? How would you find out?
> Have the people who maintained each individual building form a team that can keep an eye on sections in shifts?
How would you make this less time intensive? Can you use automation?
> If we have enough magic material, build a double wall system for breaches?
Is there a cost-benefit analysis you can run here? How would you find out? Should we keep adding walls ad infinitum or does each additional wall have diminishing returns?
It would be probably cheeper - simply because the perimeter would be shorter than the sum of perimeters for most of buildings included in the city/district. That is what cities did since at least Neolithic til moment when cities become undefendable (because of cannons and airstrike).
But that is probably not the point. In order to build wall around the city, you need to have power or consensus in society to deliver this decision. And achieve that in reasonable time might be unreal for someone in charge of one building.
I can't tell if you're asking these questions to elicit a longer discussion, or if you are doing so because you don't like the idea of a simple solution.
I'm done. Give me my paycheck.