Guide: Editing battlemap buildings

[SigniferOne]

Okay.. right... so how do you export a building ITEM into a CAS and still keep all of its textures?

EDIT: Or in other words, I haven't done this before and am now trying to figure out how to modify buildings for the first time, and all steps work properly except that all of the building's textures get lost, other than the very first one. I can see in your mod you were successfully able to edit buildings and still retain all of their textures, so perhaps you could help me out here.