Fortification

Buildings, other than walls, have too little health. Fortify would be another option when you click a building. It would increase the health of a building by 50. It would cost gold and get more expensive every time. The animation would be tiny walls surrounding the building. It would be available at level 7 town hall.

No need.
Hitpoints of every building already increase when you upgrade it. So does its graphics.

Time and resources should be spent on other game aspects, that really do need fixing.