I would use 'et to describe the forward face of the building and tlhop to describe only the area in front of it. I would think that someone who wanted to use tlhop for the forward face was overly influenced by the word front in the definition of tlhop. Would they also argue that retlh instead of Dop was correct for the side face? Probably not, because in English we don't confuse beside with side.
I don't like 'et any better than tlhop. They both refer to areas, not surfaces. I haven't found a resonably short way to comfortably refer to the front surface of a thing. Though I find that I am fine using Dop to refer to either the area of the side (not area to the side) or the surface of the side. I'll have to give more thought to why I want to treat tlhop and Dop differently.
I don't see any reason to believe that 'et fore refers to an area. A Duj 'et is the actual bow of a ship, not an area.
Now, I have a bit of a problem imagining qach 'et as the front face of a building rather than the whole front section of the building. All the rooms with windows facing front might be part of the qach 'et. I might go with qach 'et reD building's fore's exterior wall. It still seems clumsy.
I would accept qach 'et as the front face of the building or the front section. When I'm standing on the street bitching about how ugly it is, they are essentially the same, but I can see the need to differentiate, and then I'd go with David's qach 'et reD. It's no clumsier than front face of the building or the building's exterior facade facing the street. I think the front of the building in English could have the same ambiguity. The front of the building is offices, with residences at the back.