Hobie, I wish I knew. Bureaucracy and budget conspire against what we might think of as practicality everywhere. But is it totally unreasonable to build, say, a berm, for the lights to be mounted on, 200m beyond the threshold? Even if the land beyond is flat and only woods? You and I don't know the extent of airport property; perhaps those woods belong to someone else. And in so many places, 200m would put you in the middle of the sea, or of a densely populated area built up gradually many years after the runway was originally set there.
You have to keep coming back to basics, i.e. that runway lengths are known facts and that, if you're going to operate aircraft in and out of them, those facts have to be acknowleged. For better or for worse, no company can run an airline on the basis of the minimum dimensions or of the forgiving qualities of the safety envelope. If that were the case, would anyone ever have landed at Kai Tak?
Just a thought based on a local airport's movement. I live a stone's throw away from the southern threshold of SDU, Santos Dumont, the downtown Rio airport. 30m from that threshold is a pile of boulders (at the other end there's a ramp leading down into the sea, originally intended for hovercraft) and, beyond that, the sea. Thirty metres, I said. There is absolutely no room for indecision. SDU's no different from so many airports around the world; they each have their own restrictions. Like Halifax.