you mean something like this

As cool as those pictures are, I don't think that's what he means - I think he's talking about a wall that is constructed with a hole of some sort looking like it was blown out, but with then an extra layer to cover it up until the hole is created or revealed in game.

It actually sounds like something I've had to come up with working on my Shellendrak Manor build; after a first pass I decided that it needed more rooms to become more 'mansion' like, so I added some. However this left me with some rooms that had windows printed on them (formerly outside edge walls) that now butted up against another room! Solution? I printed out another blank wall piece, cut off all the tabs and simply lay it on top of the windowed wall. You could either glue it or (as I did to maintain maximum flexibility) use paperclips. Since all the ground floor rooms are held together with paperclips in the corners anyway, it doesn't actually give anything away; I think a similar solution would work for what Jedi Shep is proposing.

Those burnt out buildings are awesome! How did you go about making them? ... and did it require a great deal of Photoshop expertise?