I just did a test. For the second LOD I raised the floor of a couple hangars by 0.5m. This is more than enough to assure no flicker, at least on level ground. If such a building is placed on uneven ground, it might require a larger raising. At the transition between LODs 0 and 1, when the floor jumps up that half meter it's just perceptible as perhaps a single pixel shift, which is a heck of a lot subtler than the kinds of visual changes which typically occur at LOD transitions.
I feel confident we have a means to largely eliminate such flicker/shimmer as occurs at longer visual range: Raise the polygons.
I first tried this a number of months ago for the lowest detail, farthest LODs for buildings which are simply a horizontal rectangle placed at or near ground level. Particularly for damaged houses, where the rectangle is often placed at a very low height. I raised them about a couple meters to solve the flicker/shimmer.