Defense Buildings Inventory Button

Since the last uptade, we can now forge our defense buildings. But the only way to access the Inventory where those buildings (i.e. towers and obstacles) is removing one of them.

What about a button that allow us to access the Defense Buildings Inventory without the need of removing a building?

My suggestions about where to put that button: Castle Gate (more likely) or Tent.

Also, what about using a worker to upgrade inventored buildings?