Thanks for the reply. Regarding Artboards, are copied layers "instances" or just adding to the document size. If Symbols are the means to create an Instance, I'll have to research that.
Unfortunately is seems I'll still need two documents for my needs. Basically I have a large document that is used for a display at a venue. Then we have a second area of the same document that is used to export elements for an interactive map. Print and Web are of course differing resolutions but since the interactive map uses svg javascript interactions, it's vital to have multiple slices and the ability to have one change on the map work for differing purposes.
For instance, the small structures are all separate since they are moved to different locations each year. It would be nice to "move once" and then be able to export all our different images.