I feel like part of the initial problem is definitely the required material amounts for a wall. Making a thin wall barely costs anything, but you expand it out by one tile and it instantly doubles the required materials.
I think there should be a falloff in the required bricks depending on the wall size, so smaller walls still require around the same amount of material as they currently do, but slightly larger ones won't cost hundreds of scrap to make in comparison.
Obviously not too much of a falloff (or limit it), so it doesn't trivialize making insanely large structures that would currently cost thousands upon thousands of bricks that you definitely shouldn't be making anyway.