I know, my bad 
The defaults were actually the 5 stages of Barrack mesh. But unfortunately I forgot to push those assets. That is why they are left blank.
We also need it to take care of damaged, which is not implemented currently as I am not sure what are the damage types and how they are applied.
NOTE: You can create a new Proxy by extending the ConstructionProxy to create custom behaviour. So if nayone facny some cool effects or animated meshes…you can absolutely do it and it will still work with the construction framework.