When you add new content, based on old zones please use duplicate maps as separate files and don't just use the same map files for them all.
Modders like to make updated maps for content, and although developers are under no obligation to make allowances for this it makes it impossible to make modded maps for specific content. Since they all use the same basic map locations.
For instance Sortie uses the exact same map files as for Skirmish, and so if someone makes modded maps for Sorties they will also display in Skirmish.
