Is there a mod that could do this?
Toggling twig building in building blocked area?
If you mean a mod to remove the possibility for "raiders" to place twig on other peoples buildings then:
https://umod.org/plugins/building-blocker
I know it is unclaimed and not updated, but it currently works.
If you had something else in mind, please explain.
Actually I would like to do the opposite which is to allow. Will building blocker helps too?
No, Building Blocker will not do that.
For what you are asking I'm fresh out of ideas, sorry.
Ah thanks Fuel. No problem.