Allow the ability to renovate existing structures to renovate them and swap out materials to change the look of them.
If for balance's sake this could be restricted solely to buildings which have no inherent quality to them (No kilns, looms, etc).
Its a bit of a pain in the ass that small mistakes with the math on how much of X type of material is needed could completely ruin a certain look of a building, and we should be allowed to fix those small, easy to make mistakes.