1. I thought the CONST ZN suffix was only for segments totally disconnected from the road network during construction but expected to be reconnected at some point in the future. We do this instead of deleting them to avoid losing the road metric data they've collected, and the CONST ZN serves as note to anyone reviewing the map for disconnected segments as to why it's there and disconnected. So I'm not sure what the fuss about TTS trying to read CONST ZN is about.
2. As I understand it, there is no reliable predictability, at least within the context of WME, for which landmarks will appear, when, and for how long, or whether a particular landmark's name is displayed in any of the Waze clients. Rather they are rendered (or hidden) as a function of zoom level and other higher priority things drawn on the map around it, like other roads, their names, city names, the navigation line and its bubble names, etc. As such, denoting construction zones with landmarks does not really add any kind of reliable value to the Waze clients, but it does add extra noise to the landmarks database.
I would think that we should have a way to identify long-term construction zones in a broader sense than just temporarily re-configuring sections of roads. If fed to the Waze clients correctly, it could provider the driver with valuable information about constructions zones up ahead and maybe even a warning to keep an eye out since the map may be slightly outdated there. However, because of the way landmarks are rendered, I do not think that landmarks will adequately meet this objective.