Eureka!
I think I might have accidentally stumbled on a way to deal with the LOD issue with your roofs, if you're interested. Remember how I said that in the ideal scenario, the final LOD would just be a flat texture with AO bake to simulate the 3D elements? And remember how that was unworkable because of directional lighting and junk? Well...
OK, let's suppose you completely redid the UV unwrap in such a way that the texture now looks something like this:
And the UV unwrap, at the highest detail level, might be something like this:
Now that we've retooled the texture into one that already looks flat, we can get away with making a long-distance LOD that's literally just a flat surface. The UV looks like this, naturally:
Now here's where the lighting fix comes in. Remember the new lightmaps-on-models thing Valve added? If you enable that, in theory VRAD will sample the light hitting these spots, which are almost perfectly parallel to the roof's overall tilt:
So, in theory, the same lightmaps as if the model were just a flat surface. Which is important, because that's what the lightmap needs to look like from far away when it's
literally just a flat surface. The drawback is that you'll sacrifice any directional lighting on the sides of the pole thingies. I'd recommend a normal map, but
as YM established, those don't actually work on props that are lightmapped. (Though, as the creator of an official map, and with a more optimized version of it on the line, you might be able to persuade them to patch that issue out, as well as introducing the
static lighting improvements they added in CSGO.)
Other disclaimers: Obviously, in order to avoid the repeating-shadows bug, you'd need to either restrict the size of your roof models to the dimensions of the texture, or make bigger textures. YM's approach of storing the color and AO in separate textures and using $detailscale to tile the latter might cut down on filesize. I have no experience with modeling, so I cannot personally test any of the above theories; naturally I would have if I could.