Lack of expandibility indicates design flaws. If every inch of your level requires all sorts of Director Nodes and lighting hints and etcetera etcetera, it means you're making an extremely conrolled and quote unquote "cinematic" experience. The whole point of the AI director is that things are more dynamic on their own, so the need for maps to be so utterly complex baffles me. Either way, it's not an excuse. Plus, they already said they would release new content for L4D, such as new maps, monsters and weapons. So don't respond to an earlier promise with "Well ALL OF A SUDDEN it's not feasible."